JP4867954B2 - Semiconductor light receiving element and optical receiver - Google Patents

Description

  The present invention relates to a semiconductor light receiving element, and more particularly to an avalanche photodiode (APD), and further to an optical receiver using an avalanche photodiode (APD).

  An avalanche photodiode (APD) is a light receiving element characterized by having a signal amplification function inside compared to a PIN photodiode, a Schottky photodiode, or the like. As such an APD, an APD having an integrated structure in which functions of multiplication and light absorption are integrated, and a SAM (separated absorption and multiplication) structure having a structure in which the roles of light absorption and carrier multiplication are separated. There is.

  It is known that using an SAM type structure is effective when an APD is manufactured using a compound semiconductor. In the SAM type structure, an optimum material can be selected for each of the light absorption layer and the multiplication layer, and an APD having a higher light receiving ability and multiplication ability can be designed as compared with the integrated structure. It is.

  An example of the SAM type APD is shown in FIG.

  In the SAM type APD shown in FIG. 10, an n-type buffer layer 10-2 is formed on a semiconductor substrate 10-1, and a multiplication layer 10-3 and an electric field relaxation layer 10 are sequentially formed on the n-type buffer layer 10-2. -4, a first p-type light absorption layer 10-5, a second p-type light absorption layer 10-6, a p-type buffer layer 10-7, and a p-type contact layer 10-8.

  When light is applied to a surface incident type APD or a waveguide type APD having such a layer structure, carriers are generated in the first and second p-type light absorption layers 10-5 and 10-6, and the applied voltage is reduced. The carrier travels depending on the electric field applied to the inside, and one carrier is introduced into the multiplication layer 10-3. Carriers introduced into the multiplication layer 10-3 collide and ionize inside the multiplication layer 10-3, and a chain reaction occurs in which the generated carriers collide and ionize again. As a result, the signal carrier is avalanche multiplied (avalanche multiplied) and sent to an external electrode (or electric wire).

  As a concrete example, a report by Watanabe et al. (I Triple E Photonics Technology Letters, Vol. 675, 1993, USA) (I. Watanabe, et al., IEEE Photon. Technol. Lett., Vol. 5, pp. 675, 1993), in a SAM type APD structure formed on an indium phosphide (InP) substrate, a 0.23 μm InAlGaAs / InAlAs superlattice structure is used as a multiplication layer, and InGaAs is used as a light absorption layer. As a result, the multiplication dark current is 0.16 μA (@ M = 10), the quantum efficiency is 65% (wavelength 1.5 μm), the maximum bandwidth is 15 GHz, and the GB product is 120 GHz.

  In such a SAM type structure, the multiplication capability strongly depends on the material and structure of the multiplication layer. In particular, in the case of the same material, the multiplication characteristic is increased as the layer thickness is reduced. It is known to improve.

  For example, Makita et al., In Electronics Letter 35, 2228, 1999, in the UK (K. Makita, et al., Electron. Lett., 1999, 35, pp. 2228-2229) increased InAlGaAs / InAlAs superlattices. An example has been reported in which the GB product is improved to 200 GHz by thinning the double layer to 0.13 μm.

  As an example of thinning using InAlAs, Reno et al., I Triple E Photonics Technology Letters, Vol. 11, p. 1162 (1999) USA (C. Lenox, et al., IEEE Photon. Technol. Lett , 11, p.1162 (1999)). According to this report, the InAlAs layer is thinned to 0.2 μm, and 290 GHz is obtained as the maximum value of the GB product.

  As an example using the thinnest multiplication layer, Nii et al., I Triple E Photonics Technology Letters, Vol. 10, 409, 1998, US (H. Nie, et al., IEEE Photon. Technol. Lett., 10, p.409, (1998)). According to this report, when a SAM type APD is formed on a GaAs substrate, a multiplication layer is formed using Al (0.2) Ga (0.8) As, and the layer thickness is reduced to 80 nm. Yes. Thereby, 290 GHz is obtained as the maximum value of the GB product.

  FIG. 11 shows an example of a conventional APD optical receiver.

  In the APD optical receiver, as shown in FIG. 11, the signal introduced from the optical fiber 11-1 is input to the APD 11-3 through the lens 11-2. The APD 11-3 is connected to the preamplifier 11-4, and the signal input to the APD 11-3 is output to the high frequency connector 11-6 through the microstrip line (MSL) 11-5.

The reception sensitivity of a 10 Gb / s signal is expressed by the light intensity that gives a bit error rate (BER) of 1 × 10 ⁻⁹ when 23 stages of pseudo random signal (Pseudo random bit stream = PRBS) are transmitted.

  For example, the following are known results of reception sensitivity evaluation in the 10 Gb / s band.

  Tseng et al. (I Triple E Photonics Technology Letters, Vol. 8, p. 1229, 1996, USA) (LD Tzeng, et. Al., IEEE Photon. Technol. Lett., Vol.8, p .1229, 1996), receiving sensitivity of -28.7 dBm is obtained, and Yun et al. Report (I Triple E Photonics Technology Letters, Vol. 8, p. 1232, 1996, USA) ( In TY Yun, et. Al., IEEE Photon. Technol. Lett., Vol.8, p.1232, 1996), a receiving sensitivity of −28.5 dBm is obtained.

  Many 40-Gb / s optical receivers using PIN-PD have been reported, but no receiver using APD has been reported so far.

  Conventionally reported receivers for 40 Gb / s are those in which a high frequency amplifier is connected to a PIN-PD, but in order to receive a modulated signal, many optical inputs of about 0 dBm or more are required. .

  FIG. 12 is a block diagram showing an example of a conventional optical receiver using an optical preamplifier.

  The optical receiver shown in FIG. 12 includes an optical preamplifier 12-3, a PIN-PD optical receiver 12-4, an optical fiber 12- that connects the optical preamplifier 12-3 and the PIN-PD optical receiver 12-4. 1 and.

  The optical preamplifier 12-3 and the PIN-PD optical receiver 12-4 constitute an optical receiver 12-6.

  The optical signal 12-2 input to the optical receiver 12-6 via the optical fiber 12-1 is output from the optical receiver 12-6 as an electrical signal 12-5.

  As shown in FIG. 12, in the conventional optical receiver 12-6, an optical preamplifier 12-3 using a fiber amplifier or the like is arranged in the previous stage, and after amplifying the received light, the PIN-PD optical receiver 12- The optical preamplifier 12-3 is an indispensable component.

  As seen in the prior art, thinning the multiplication layer is very effective from the viewpoint of improving the GB product, but it also causes dark current deterioration at the same time. In order to suppress the multiplication dark current, it is desirable that the band gap of the multiplication layer is large.

  As an example of a SAM type APD on a GaAs substrate, a multiplication layer having a thickness of 80 nm is formed using Al (0.2) Ga (0.8) As to improve the GB product. It has been described in the report of Nii et al. That 290 GHz was obtained as the maximum value.

  On the other hand, among the lattice-matching materials on the InP substrate, InAlAs is generally known as the material that gives the widest gap.

  When the multiplication layer is formed using InAlAs, for example, an example in which the layer thickness is 0.2 μm is described in the report of Reno et al. In this example, a GB product as high as 290 GHz is obtained as the maximum value of the GB product, but M is a value of 30 or more, and in the case of M = 1 to 15 which is a practical range when applied to optical communication, GB is obtained. The maximum value of the product is about 150 GHz.

  In order to further improve the GB product obtained in the vicinity of M = 1 to 15, a multiplication layer capable of obtaining a high GB product value together with a device design having a high maximum bandwidth is required.

  Thus, it is conceivable to use InAlAs as the multiplication layer material and reduce the film thickness to improve the GB product.

  However, when the thickness of the multiplication layer is reduced to less than 0.1 μm, the dark current deterioration becomes noticeable. When the dark current deterioration becomes significant, the effect of improving the GB product by thinning the film is lost.

  Therefore, when InAlAs is used, when a multiplication layer of less than 0.1 μm is used, the GB product is deteriorated as compared with the case of using a multiplication layer having a thickness of 0.1 μm or more. .

  As a result, when an optical receiver having a bit rate of 2.5 Gb / s to 40 Gb / s is configured using such a thin film APD, the light configured using a multiplication layer having a layer thickness of 0.1 μm or more. The sensitivity is reduced compared to the receiver.

  For this reason, in the APD using the thinned multiplication layer, although the signal multiplication function remains, the multiplication characteristic leading to the improvement in sensitivity has not been obtained. Therefore, an optical receiver having a structure using an APD having a high GB product of 200 GHz or more and a preamplifier cannot be realized.

  Even in the case of reducing the thickness, in the conventional structure, both sides of the multiplication layer are made of the same band gap material as the multiplication layer or a lower band gap material than the multiplication layer.

  When a voltage is applied to the SAM type APD, as shown in FIG. 13, an electric field capable of multiplication is also applied to the layers 13-3 and 13-5 adjacent to the multiplication layer 13-4. As a result, when the thickness of the multiplication layer 13-4 is reduced to 0.1 μm or less, depletion occurs with a layer thickness that cannot be ignored depending on the concentration of the adjacent layers 13-3 and 13-5. End up. Thereby, the width 13-6 of the effective multiplication region becomes wider than the thickness of the multiplication layer 13-4, and the effect of reducing the thickness of the multiplication layer 13-4 is reduced.

For example, when the concentration of the layers 13-3 and 13-5 adjacent to the multiplication layer 13-4 is 1 × 10 ¹⁷ cm ⁻³ , it depends on the layer thickness and material of the multiplication layer 13-4. The layer thickness required for electric field relaxation is estimated to be 0.5 μm or more.

  In such a case, even if the multiplication layer 13-4 having a layer thickness of less than 0.1 μm is produced, the multiplication actually occurs with a width of 0.2 to 0.3 μm, and the thickness is reduced. The effect of cannot be demonstrated effectively.

As described above, in the conventional optical receiver, an APD having a high GB product and a low dark current has not been obtained. Therefore, the limit of the reception sensitivity of the APD optical receiver at 10 Gb / s is −28 to It was about -29 dBm (bit error rate (BER) 1 × 10 ⁻⁹ , pseudo random signal (PRBS) evaluated at 23 stages).

  This is not determined by the shot noise limit, and does not approach the theoretical sensitivity limit of the APD receiver.

  In a conventional optical receiver using a 40 Gb / s PIN-PD and a preamplifier IC, the reception sensitivity is very low, and high light intensity is required for reception. For this reason, an optical amplifier using a fiber amplifier or the like is arranged in the front stage of the optical receiver and configured as an optical preamplifier, so that the function as an optical receiver is achieved as a whole.

  In this optical receiver, an input level required for the optical receiver is required to be about 0 dBm, and the power consumption of the fiber amplifier is increased.

  The present invention has been made in view of the above-described problems in the conventional semiconductor light-receiving element and the optical receiver using the same, and is a thin-film multiplication layer having a high GB product and darkness. An object of the present invention is to provide a multiplication layer having a multiplication characteristic with a low current, to provide a high-speed and high-sensitivity semiconductor light-receiving element including the multiplication layer, and an optical receiver using the semiconductor light-receiving element.

In order to achieve this object, the present invention includes a substrate, a multiplication layer formed on the substrate, and a multiplication inhibition layer formed on both sides of the multiplication layer, and the multiplication inhibition layer. , to the multiplication layer of less than 0.1 [mu] m, to provide a semiconductor light receiving element characterized in der Rukoto which prevents effective multiplication layer thickness is increased.

  As a material of the multiplication layer, for example, In (x) Al (1-x) As (0 ≦ x <0.52) can be used.

  The value of x in the above In (x) Al (1-x) As (0 ≦ x <0.52) can be determined according to the following equation.

(1-x) ≧ k ₁ log 10 (dm) + k ₂

However, k ₁ is an arbitrary value satisfying k ₁ ≦ −0.3, and k ₂ is determined so that the curve of the above equation passes through the point (dm = 0.1, x = 0.52). Shall.

  As a material for the multiplication layer, Si, GaN, AlN, InN, AlP, AlAs, GaP, AlSb or a compound thereof (AlGaN, InGaN, AlInN, InAlGaN, GaP, AlGaP, AlAsP, AlGaAsP, AlAsSb, etc.) is selected. be able to.

Even when these materials are used, if dark current deterioration accompanying an increase in the multiplication electric field is unavoidable, the multiplication layer preferably has a layer thickness of 0.02 μm or more.

  The semiconductor light receiving element described above can be configured as an avalanche photodiode (APD).

The layer thickness of the multiplication layer may be 0.01 μm or more and less than 0.1 μm.

  This semiconductor light receiving element can be configured as, for example, a SAM (separated absorption and multiplication) type avalanche photodiode (APD).

Furthermore, the substrate was indium phosphide (InP) substrate, the multiplication preventing layer may be made of In (x) Al (1- x) As (x ≦ 0.4).

  For example, the multiplication inhibiting layer can be configured as a semiconductor layer made of a material having a wider gap than the material forming the multiplication layer.

  The layer thickness of the multiplication inhibiting layer is preferably substantially the same as the layer thickness of the multiplication layer.

  For example, the multiplication inhibiting layer is set to have a thickness of 0.02 μm or more and 0.1 μm or less.

  For example, the multiplication inhibiting layer can be made of AlAs.

The concentration of the multiplication inhibiting layer is preferably 1 × 10 ¹⁷ cm ⁻³ or more depending on the undoped or arbitrary doping amount.

  In order to take advantage of the high-speed characteristics of the thin film multiplication layer, when an APD is manufactured using this layer structure, the pn junction area should be about 1000 square μm or less so as to reduce the junction capacitance and to make the APD with a large CR limiting speed. preferable.

  By connecting such a high light-gap semiconductor light-receiving element and a preamplifier IC, an APD receiver having a higher sensitivity than a conventional optical receiver can be configured in a band of 2.5 Gb / s to 40 Gb / s. it can.

  That is, the present invention provides an optical receiver comprising the above-described semiconductor light receiving element and a preamplifier IC connected to the semiconductor light receiving element.

The present invention also includes the above-described semiconductor light-receiving element and a preamplifier IC connected to the semiconductor light-receiving element, and the light sensitivity giving a bit error rate (BER) of 1 × 10 ⁻⁹ is −26 dBm or less. An APD optical receiver for communication with 10 Gb / s is provided.

Furthermore, the present invention includes the above-described semiconductor light-receiving element and a preamplifier IC connected to the semiconductor light-receiving element, and the light sensitivity giving a bit error rate (BER) of 1 × 10 ⁻⁹ is −7 dBm or less. An APD receiver for 40 Gb / s communication is provided.

  That is, in the case of an optical receiver in which an optical preamplifier is arranged in the preceding stage, the present invention reduces the amplification amount of the optical preamplifier within the range in which the reception sensitivity is improved by the present invention. Alternatively, the optical receiver is configured by omitting the optical preamplifier itself.

  In the multiplication layer having a thickness of less than 0.1 μm produced on the InP substrate according to the present invention, carrier multiplication occurs inside the thin multiplication layer, leading to generation of a large number of carriers in a short time, and high GB Product can be provided.

  Further, since it is made of a material having a wider gap than a conventionally considered material, the multiplication dark current is suppressed to 0.1 to 1 μA or less, and at most 2 μA or less, and this layer structure is obtained. A semiconductor light receiving element such as an APD can be used as a high sensitivity light receiving element in the range of 2.5 to 40 Gbps.

Since the multiplication probability is greatly reduced inside the multiplication suppression layer, it is possible to prevent the effective multiplication layer thickness from spreading due to the spread of the depletion layer, and carriers are selectively multiplied only inside the multiplication layer. Wake up.

When the doping concentration of the multiplication inhibiting layer is 1 × 10 ¹⁷ cm ⁻³ or more, there is an effect of electric field relaxation, and multiplication in a layer adjacent to the multiplication inhibiting layer on the side opposite to the multiplication layer is performed. Is reduced.

  By connecting a semiconductor light receiving element such as an APD thus manufactured to a preamplifier IC, it functions as a high sensitivity receiver in a band of 2.5 Gb / s to 40 Gb / s.

  For example, when receiving light in the 1.5 μm band, assuming that the conversion efficiency is T (A / W), the multiplication factor M, and the transimpedance of the preamplifier is AΩ, the conversion efficiency of T · M · A (V / W) is A receiver is configured.

  In the case of an optical receiver in which an optical preamplifier is arranged at the front stage, the power corresponding to the increase in the reception sensitivity at the rear stage can be omitted by the present invention. Even when the entire optical preamplifier is omitted, since reception sensitivity is improved, there is no problem in receiving an optical signal.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 shows a structure of a semiconductor light receiving element according to a first embodiment of the present invention. In the present embodiment, the semiconductor light receiving element is formed as a SAM type APD formed on a semiconductor substrate.

  This SAM type APD includes a semiconductor substrate 1-1, an n-type buffer layer 1-2, a multiplication layer 1-3, an electric field relaxation layer 1-4, and a first p formed on the semiconductor substrate 1-1 in this order. The light-absorbing layer 1-5, the second p-type light absorbing layer 1-6, the p-type buffer layer 1-7, and the p-type contact layer 1-8.

  As the layer structure of the SAM type APD according to the present embodiment, a p-type buffer layer 1-7 is first formed on the semiconductor substrate 1-1, and the first p-type is formed in this order on the p-type buffer layer 1-7. A structure in which a light absorption layer 1-5, a second p-type light absorption layer 1-6, an electric field relaxation layer 1-4, a multiplication layer 1-3, an n-type buffer layer 1-2, and an n-type contact layer 1-8 are stacked. It is also possible.

  The p-type impurity concentration of the first p-type light absorption layer 1-5 is set lower than the p-type impurity concentration of the second p-type light absorption layer 1-6. The layer thickness of the first p-type light absorption layer 1-5 is in the range of 0.01 μm to 2 μm, and the layer thickness of the second p-type light absorption layer 1-6 is in the range of 0 μm to 0.5 μm. Make it.

  If the layer thickness of the light absorption layers 1-5 and 1-6 is too thick, the traveling time of carriers becomes long, and high speed and high sensitivity characteristics cannot be obtained. For this reason, the above-mentioned range was set as the range of the layer thickness capable of obtaining high speed and high sensitivity characteristics.

  The thin film multiplication layer 1-3 is formed with as low an impurity concentration as possible in order to uniformly apply an electric field. The layer thickness of the thin film multiplication layer 1-3 is less than 0.1 μm from the viewpoint of improving the GB product, and 0.02 μm or more from the viewpoint of suppression of multiplication dark current.

  However, when the multiplication layer 1-3 is formed of InAlAs lattice-matched to InP in an APD configured with such a thin film multiplication layer 1-3 on, for example, an InP substrate, the multiplication dark current increases. However, compared to shot noise in which a signal current is generated in a transmission band of 2.5 Gb / s to 40 Gb / s, a noise component equal to or higher than that is generated, and high sensitivity cannot be expected.

  Therefore, In (x) Al (1-x) As (1-x> 0.48) in which the Al composition of InAlAs is increased is used as a material for further reducing the dark current.

  In general, when lattice mismatched materials on a substrate are laminated in this way, strain is introduced into the laminated layer up to the critical thickness, but if a layer thickness greater than that is laminated, lattice defects are introduced and lattice relaxation occurs. Is known to occur.

  However, the present inventor has shown by experiment that In (0.52) Al (0...) Is introduced when crystal defects due to lattice relaxation caused by laminating lattice mismatch materials to a critical thickness or more are introduced. 48) In the case of a material having a wider gap than As, when this material was applied to an APD multiplication layer, the multiplication characteristics were not affected, and the multiplication dark current was also suppressed. From this, it was understood that the application of the wide gap material is effective for the multiplication layer or the layer structure for forming other light receiving elements.

  If it is desired to design a small amount of lattice mismatch, it is possible to design the aluminum composition to be increased in inverse proportion to the film thickness dm.

  For example, the composition of In (x) Al (1-x) As can be determined according to the following equation.

(1-x) = k ₁ · log 10 (dm) + k ₂ · 0.01 <dm <0.1, k ₁ <−0.3

  However, it is determined that the curve represented by the above formula passes through dm = 0.1 and (1-x) = 0.48.

In order to minimize the deviation from the lattice matching fabrication conditions and obtain the effect sufficiently, as shown by 2-1 in FIG. 2, k ₁ = −0.3, and the multiplication layer thickness is 0.1 μm. It is effective to determine the coefficient k ₂ so that the composition in this case is lattice matched, that is, (1-x) = 0.48 when dm = 0.1. In this case, k ₂ = 0.18.

However, even if the amount of lattice mismatch increases, there is no problem if it shifts to the wide gap side. In practice, it may be produced with an Al composition larger than the Al composition determined by the above equation. That is, the composition when k ₁ ≦ −0.3 and the multiplication layer thickness is 0.1 μm is lattice matched, that is, x = 0.52 when dm = 0.1. The coefficient k ₂ should be determined. This corresponds to the range indicated by 2-2 in FIG.

  Thus, the multiplication characteristic is not affected by the lattice relaxation, and if the gap is sufficiently wide compared to In (0.52) Al (0.48) As, the multiplication characteristic can be obtained. By utilizing this, GaN, AlN, AlN, InN, AlP, GaP, and a material in which these materials are combined at an arbitrary mixing ratio can be used as the material of the thin film multiplication layer.

The electric field relaxation layer 1-4 contains a p-type impurity and is made of the same material as the light absorption layers 1-5 and 1-6 and the multiplication layer 1-3. The thickness of the electric field relaxation layer 1-4 is about 0.02 to about 0.2 μm and has a p-type impurity concentration of 0.5 × 10 ^{18 to} 2 × 10 ¹⁸ cm ⁻³ .

The n-type buffer layer 1-2 has an n-type impurity concentration of 1 × 10 ^{17 to} 1 × 10 ²⁰ cm ⁻³ and a layer thickness of about 0.1 to about 0.5 μm.

  In order to improve the punch-through characteristics of the photocurrent, it is necessary to alleviate the band discontinuity between the n-type buffer layer 1-2 and the light absorption layers 1-5 and 1-6. For this purpose, a quaternary layer, an InP layer, or a thin film barrier layer using a tunnel effect may be inserted between the n-type buffer layer 1-2 and the light absorption layers 1-5 and 1-6.

  Using the layer structure thus configured, an APD having a structure in which the maximum band can be applied to approximately 10 Gb / s or 40 Gb / s is manufactured. In this case, it is effective to design the pn junction area to 1000 square μm or less in order to avoid the CR limitation regarding the frequency response, in which the pn junction capacitance is an important parameter.

  Each APD is connected to a high-speed amplifier corresponding to the band, and can be used as a high-sensitivity optical receiver at 10 Gb / s or 40 Gb / s. At 40 Gb / s, the operating power of the optical preamplifier can be reduced, or the entire optical preamplifier can be omitted.

(Second embodiment)
In the second embodiment, a SAM type APD is configured as a semiconductor light receiving element.

The structure of the SAM type APD according to this embodiment is shown in FIG. The SAM APD according to the present embodiment includes a semiconductor substrate 3-18, an n-type buffer layer 3-17 formed in this order on the semiconductor substrate 3-18, a first multiplication suppression layer 3-16, Multiplication layer 3-15, second multiplication suppression layer 3-14, electric field relaxation layer 3-13, p ⁻ type light absorption layer 3-12, p ⁺ type light absorption layer 3-11, p A type buffer layer 3-10 and a p-type contact layer 3-9.

On the other hand, FIG. 3A shows the structure of a conventional SAM type APD. A conventional SAM type APD includes a semiconductor substrate 3-8, an n-type buffer layer 3-7 formed on the semiconductor substrate 3-8 in this order, a multiplication layer 3-6, and an electric field relaxation layer 3-5. And a p ⁻ type light absorption layer 3-4, a p ⁺ type light absorption layer 3-3, a p type buffer layer 3-2, and a p type contact layer 3-1.

  In the SAM type APD according to the present embodiment, the semiconductor substrate 3-18 uses GaAs or InP.

The p ⁺ type light absorption layer 3-11 is set to have a higher impurity concentration than the p ⁻ type light absorption layer 3-12. The layer thickness of the p ⁺ -type light absorption layer 3-11 is set in the range of 0.0 μm or more and 0.5 μm or less, and the layer thickness of the p ⁻ -type light absorption layer 3-12 is in the range of 0.01 μm or more and 2 μm or less. Is set to

  If the layer thickness of the light absorption layers 3-11 and 3-12 is too thick, the traveling time of carriers becomes long, and high speed and high sensitivity characteristics cannot be obtained. For this reason, the above-mentioned range was set as the range of the layer thickness capable of obtaining high speed and high sensitivity characteristics.

  The band gaps of the light absorption layers 3-11 and 3-12 are selected from those having a small band gap, and are designed so as to receive a wide range of wavelengths as much as possible.

The light absorption layers 3-11 and 3-12 can also be configured as n ⁺ and n ⁻ type light absorption layers, respectively.

  The light absorbing layers 3-11 and 3-12 may be made of In (0.53) Ga (0.47) As when formed on an InP substrate, and In (0.5) when formed on a GaAs substrate. 0.1) Ga (0.9) As or the like is used.

  The multiplication layer 3-15 is made as low as possible in order to uniformly apply an electric field. The layer thickness is less than 0.1 μm from the viewpoint of improving the GB product, and 0.01 μm or more from the viewpoint of preventing dark current deterioration.

  In the conventional SAM type APD shown in FIG. 3A, the layers constituting both sides of the multiplication layer 3-06, that is, the electric field relaxation layer 3-05 and the n-type buffer layer 3-07 are the multiplication layer 3. It is made of a material having the same band gap as −06 or a band gap smaller than that of the multiplication layer 3-06. For this reason, in the structure of the conventional SAM type APD, when a high electric field portion is spread by applying a voltage, the actual effective multiplication layer thickness is widened.

  On the other hand, in the SAM type APD according to the second embodiment, multiplication suppression layers 3-14 and 3-16 having a very low probability of avalanche multiplication are provided on both sides of the multiplication layer 3-15. Thus, the spread of the effective multiplication layer thickness can be prevented.

  The multiplication suppression layers 3-14 and 3-16 are configured using a material having a higher breakdown electric field than the multiplication layer 3-15.

  In general, the multiplication electric field has a layer thickness dependency when the band gap is the same (depending on the band gap when the band thickness is the same), so that the band gap is 110 with respect to the multiplication layer 3-15. It is desirable to use a material that has about%.

  The layer thicknesses of the multiplication inhibiting layers 3-14 and 3-16 are equal to or thinner than the layer thickness of the multiplication layer 3-15.

  However, the effect can be increased by setting the layer thicknesses of the multiplication inhibiting layers 3-14 and 3-16 to 0.02 μm or more.

  Further, if the band gap difference is sufficient, the multiplication electric field of the multiplication inhibition layers 3-14 and 3-16 becomes sufficiently high, so that the thickness of the multiplication inhibition layers 3-14 and 3-16 is increased. It can be thicker than 15.

  By inserting the multiplication inhibition layers 3-14 and 3-16, the probability that avalanche multiplication occurs in the thin film multiplication layer 3-15 is increased, and adjacent multiplication inhibition layers 3-14 and 3-16 are increased. The probability of multiplication can be lowered. Therefore, the main multiplication of the multiplication carrier can be confined inside the multiplication layer 3-15.

In the multiplication inhibiting layers 3-14 and 3-16, in order to prevent a multiplication from occurring due to a high electric field applied to the outside of the multiplication inhibiting layers 3-14 and 3-16, a layer thickness of 0.1 μm is 1 ×. 10 ¹⁷ cm ⁻³ or more, layer thickness of 0.05 μm, 2 × 10 ¹⁷ cm ⁻³ or more, layer thickness of 0.02 μm, concentration of 5 × 10 ¹⁷ cm ⁻³ or more, and intermediate layer thickness of these layers A higher effect can be expected by designing to have a concentration equal to or higher than the concentration obtained by complementing the concentration. In this case, the multiplication suppression layers 3-14 and 3-16 also serve as the electric field relaxation layer 3-13.

(Third embodiment)
Since the band gap of the lattice-matching material is well known, it is easy to calculate the composition from the band gap and determine the layer structure.

  In the case of a SAM type APD configured on an InP substrate, In (0.52) Al (0.48) As is known as a wide gap material as a material system for lattice matching.

  A multiplication inhibiting layer for this cannot be formed because a lattice-matching material with a band gap of 110% or more is not known.

  Therefore, a lattice-mismatched wide gap material is used. For example, using In (x) Al (1-x) As (x <0.52) is equivalent to being able to be sandwiched with a wider gap material than InAlAs, and increases the effective multiplication layer thickness. Can be prevented.

  Here, the In (x) Al (1-x) As (x <0.52) formed on the InP substrate, particularly the band gap when a layer thickness sufficient to cause lattice relaxation is obtained. Therefore, it is not easy to design the composition of the material from the viewpoint of the band gap.

  When estimated from the standpoint of multiplication dark current, 0.06 μm In (0.4) Al (0.6) As is compared to 0.1 μm In (0.52) Al (0.48) As. It is known that the band gap difference can be seen sufficiently.

  Therefore, this In (0.4) Al (0.6) As can be used as a multiplication suppression layer for the InAlAs multiplication layer.

  In addition, since there is no harmful effect even when the Al composition is increased over this material, In (x) Al (1-x) As, (1-x> 0.6), and a layer thickness of 0.06 μm are used. If a multiplication suppression layer is configured, the effect of multiplication suppression can be expected.

  In particular, when the multiplication inhibition layer is made of AlAs, the effect of multiplication inhibition can be further expected, and the layer thickness may be 0.02 μm.

At this time, if the concentration of the n-side multiplication inhibiting layer is 1 × 10 ¹⁷ cm ⁻³ or more, the electric field is relaxed, and the multiplication inhibiting effect in the layer adjacent to the multiplication inhibiting layer is also obtained.

  Based on the layer structure thus obtained, an APD having a high speed and a high GB product can be obtained.

  These APDs can also be expected to be applied to high sensitivity receivers. In particular, by connecting the APD to a preamplifier, it is an ultra-sensitive receiver in a band such as 10 Gb / s, and an optical receiver similar to a conventional PIN-PD receiver in a band of 40 Gb / s, but more It can be used as a highly sensitive receiver.

  In particular, when applied to the 40 Gb / s band, it is possible to save power by suppressing the multiplication factor of the optical preamplifier disposed in front, and in particular, a 40 Gb / s transmission system that does not use an optical preamplifier at a short distance is configured. It becomes possible to do.

According to the above embodiment , the APD having a multiplication layer thickness of less than 0.1 μm on the InP substrate has a GB product in the range of M = 1 to 15 compared with the APD having a layer thickness of 0.1 μm or more. At the same time, the level of the multiplication dark current can be suppressed to a low level of 0.1 to 1 microampere or less.

  By obtaining such a high GB product, in 2.5 Gb / s or 10 Gb / s communication, it is possible to obtain practical characteristics even in a multiplication region where M> 10.

  Further, for example, by designing such that the quantum efficiency is 50% or more and the maximum band exceeds 40 GHz, such as a waveguide structure, the structure can be applied to 40 Gb / s.

Further, by introducing a multiplication inhibiting layer, it is possible to prevent expansion of the multiplication region and further improve the GB product for a thin film multiplication layer of 0.1 μm or less. When doping is applied to the multiplication inhibiting layer, particularly when it is set to 1 × 10 ¹⁷ cm ⁻³ or more, multiplication is performed inside the layer in contact with the multiplication inhibiting layer on the side opposite to the multiplication layer. The probability of performing can be reduced, and the effect of improving the GB product is further enhanced.

  By obtaining an APD having such a high GB product, an APD receiver having a reception sensitivity closer to the shot noise limit can be realized in 10 Gb / s optical communication.

  For example, when an APD having a bandwidth of fc> 10 GHz and a quantum efficiency η> 80% is connected to a preamplifier having a transimpedance of 1 KΩ, a reception sensitivity of −29 dBm or higher can be obtained.

  Also, considering the yield of assembly or the like, about -26 dBm is obtained.

  In addition, a 40 Gb / s band APD receiver, which is unprecedented, can be realized. This 40 Gb / s APD receiver can reduce the amount of amplification of the optical preamplifier in the previous stage due to its characteristics, or the optical preamplifier itself can be omitted. This is effective in reducing the large power consumption of the optical preamplifier. As a result, a low power consumption 40 Gb / s optical receiver can be configured.

  This example corresponds to the first embodiment.

  FIG. 4 is a diagram of the layer structure of the semiconductor light receiving element according to the first embodiment. The semiconductor light receiving element according to this embodiment is configured as an APD.

  The APD according to Example 1 includes an n-type indium phosphide (InP) substrate 4-1, and an n-type InP buffer layer 4-2 (layer) formed in this order on the n-type indium phosphide (InP) substrate 4-1. A thickness of 1 μm), an n-type InAlAs buffer layer 4-3 (layer thickness of 0.5 μm), an In (0.4) Al (0.6) Asn-type buffer layer 4-4 (layer thickness of 0.05 μm), In (0.4) Al (0.6) As multiplication layer 4-5 (layer thickness 0.05 μm) and first p-type In (0.4) Al (0.6) As electric field relaxation layer 4-6 (Layer thickness 0.05 μm), second p-type InAlGaAs electric field relaxation layer 4-7 (layer thickness 0.05 μm), first p-type InGaAs light absorption layer 4-8 (layer thickness 1 μm), and second p-type InGaAs light Absorption layer 4-9 (layer thickness 0.1 μm), p-type InP buffer layer 4-10 (layer thickness 1 μm), p-type In aAs contact layer 4-11 and (layer thickness 0.5 [mu] m), consists.

  Each of these layers is formed using a crystal growth apparatus.

  Based on this layer structure, a surface incident type high-speed and high-sensitivity APD as shown in FIG. 5 was produced.

  Hereinafter, a method for manufacturing the APD shown in FIG. 5 will be described.

  First, a mesa having a diameter of 20 μm and a height of 3 to 5 μm is formed using wet etching (such as a bromine system) or dry etching (such as RIE). As a result, a mesa having the APD layer structure 5-4 is formed.

  In this case, the mesa area is approximately equal to the pn junction area, which is approximately 314 square μm.

  Next, a passivation film is formed using polyimide.

  Next, a p-type contact electrode 5-6 and an n-type contact electrode 5-5 are formed on the top surface of the p-type contact layer 4-11 and the mesa bottom surface where the n-type layer is exposed.

  Next, using Ti / Pt / Au, a p-electrode 5-7 and an n-electrode 5-8 are formed so as to cover the contact electrodes 5-5 and 5-6.

  At this time, the n-electrode 5-8 is wired so as to be drawn from the n-type contact electrode 5-5 to the surface.

  The APD layer structure 5-4 is formed on the InP substrate 5-3, and an antireflection film 5-2 is formed on the surface of the InP substrate 5-3 opposite to the APD layer structure 5-4. ing. The signal light 5-1 is incident on the APD layer structure 5-4 through the antireflection film 5-2.

  When the characteristics of this device were evaluated, the breakdown voltage was 20 V and the multiplication dark current was 0.5 μA. The quantum efficiency was 80%. The maximum response frequency was 10 GHz with a 50Ω load, and the GB product was 220 GHz. In particular, the frequency response at a multiplication factor M = 2 to 20 was maintained at 10 GHz.

  When the APD according to this example and a preamplifier having a transimpedance of 1 KΩ or more were connected and the frequency characteristics were evaluated, a band of 10 GHz was obtained.

The optical receiver is configured using the APD and the preamplifier according to the present embodiment, and the reception sensitivity is evaluated at a bit rate of 10 Gb / s. When a 23-stage pseudo random signal is used, the bit error rate (BER) is 1 The light intensity giving x10 ^-9 was -30 dBm.

  In addition, when a large number of optical receivers composed of APDs and preamplifiers according to this example were manufactured in succession, variations in reception sensitivity due to differences in coupling efficiency and slight differences in mounting conditions were observed.

  According to the statistics at this time, the average reception sensitivity of the receiver is -29 dBm, and even the lowest one can secure -26 dBm. This is a very sensitive APD optical receiver for 10 Gb / s.

  This example corresponds to the first embodiment.

  FIG. 6 is a diagram of the layer structure of the semiconductor light receiving element according to the second embodiment. The semiconductor light receiving element according to this embodiment is configured as an APD.

  The APD according to Example 2 includes an SI type indium phosphide (InP) substrate 6-1 and an n type InP buffer layer 6-2 (layer) formed on the SI type indium phosphide (InP) substrate 6-1 in this order. N-type InAlGaAs intermediate refractive index layer 6-3 (0.5 μm), n-type In (0.4) Al (0.6) As buffer layer 6-4 (layer thickness 0.05 μm), , In (0.4) Al (0.6) As multiplication layer 6-5 (layer thickness 0.05 μm) and first p-type In (0.4) Al (0.6) As electric field relaxation layer 6- 6 (layer thickness 0.05 μm), a second p-type InAlGaAs electric field relaxation layer 6-7 (layer thickness 0.05 μm), a first p-type InGaAs light absorption layer 6-8 (layer thickness 0.4 μm), and a second p Type InGaAs light absorption layer 6-9 (thickness 0.1 μm) and p type InAlGaAs intermediate refractive index layer 6-10 (0 0.5 μm), a p-type InP cladding layer 6-11 (layer thickness 2 μm), and a p-type InGaAs contact layer 6-12 (layer thickness 0.5 μm).

  Each of these layers is formed using a crystal growth apparatus.

  In this embodiment, a waveguide type APD as shown in FIG. 7 is configured using the layer structure shown in FIG.

  Hereinafter, a method of manufacturing the waveguide type APD shown in FIG. 7 will be described.

  First, an APD mesa 7-2 having a length of 10 μm, a width of 5 μm, and a height of 4 to 5 μm is formed using wet etching (such as a bromine system) or dry etching (such as RIE).

  An n-electrode mesa 7-3 having a height of about 2 to 3 μm is formed by wet or dry etching, leaving a region for forming an n-type contact electrode around the APD mesa 7-2. In this case, the area of the APD mesa 7-2 is equal to the pn junction area, and is approximately 50 square μm.

  Next, a passivation film is formed using polyimide or a nitride film.

  Contact electrodes are formed on the upper surface of the p-type contact layer 6-12 and the upper surface of the APD mesa 7-2 from which the n-type layer is exposed.

  A contact electrode made of Ti / Pt / Au is formed so as to cover the n electrode 7-4 and the p electrode 7-5.

  The n-electrode 7-4 and the p-electrode 7-5 have a shape in which a coplanar line or a microstrip line or a combination of both is connected.

  FIG. 7 shows the case of a coplanar line.

  In this case, a metal constituting the ground is formed on the back surface of the substrate on which the element is formed by vapor deposition or the like.

  Further, an antireflection film 7-6 is formed on the side surface of the substrate, and the signal light 7-1 is incident on the waveguide type APD through the antireflection film 7-6.

  When the characteristics of this device were evaluated, the breakdown voltage was 12 V and the multiplication dark current was 0.5 μA. The quantum efficiency was 70%. The maximum response frequency was 40 GHz with a 50Ω load, and the GB product obtained a maximum of 220 GHz. In particular, the frequency response at the multiplication factor M = 2 to 5 was maintained at 36 GHz or more.

  When the frequency characteristics were evaluated by connecting the waveguide type APD according to the present example and a preamplifier having a transformer impedance of 100Ω, a band of 40 GHz was obtained.

Further, when the receiver is configured using the waveguide type APD and the preamplifier according to the present embodiment and the reception sensitivity is evaluated at a bit rate of 40 Gb / s, the bit error rate is obtained when a 23-stage pseudo random signal is used. The light intensity giving (BER) 1 × 10 ⁻⁹ was −10 dBm. This is a high sensitivity optical receiver for 40 Gb / s.

  Similar to the first embodiment, a large number of optical receivers composed of the waveguide type APD and the preamplifier according to the present embodiment were continuously configured and evaluated. 7 dBm could be obtained.

  When this APD optical receiver was used, the output of the fiber amplifier connected as an optical preamplifier could be reduced by 3 dB, and the power consumption was 1 W, but it could be reduced to approximately half, 0.5 W.

  When an optical fiber transmission line of about 10 km or shorter was used, a signal of 40 Gb / s could be received without an optical preamplifier.

  This example corresponds to the second embodiment.

  FIG. 8 is a diagram of the layer structure of the semiconductor light receiving element according to the third embodiment. The semiconductor light receiving element according to this embodiment is configured as an APD.

  The APD according to Example 3 includes a gallium arsenide (GaAs) substrate 8-1 and an n-type Al (0.2) Ga (0.8) formed in this order on the gallium arsenide (GaAs) substrate 8-1. As buffer layer 8-2 (layer thickness 1 μm), n-type Al (0.12) Ga (0.88) As intermediate refractive index layer 8-3 (layer thickness 0.5 μm), and AlAs multiplication inhibiting layer 8 -4 (layer thickness 0.05 μm), Al (0.2) Ga (0.8) As multiplication layer 8-5 (layer thickness 0.05 μm), and AlAs multiplication inhibition layer 8-6 (layer thickness) 0.05 μm), a p-type Al (0.2) Ga (0.8) As electric field relaxation layer 8-7, and a first p-type In (0.1) Ga (0.9) As light absorption layer 8- 8 (layer thickness 0.2 μm), the second p-type In (0.1) Ga (0.9) As light absorption layer 8-9 (layer thickness 0.1 μm), and p-type Al (0.12) Ga. (0 88) As intermediate refractive index layer 8-10 (layer thickness 0.5 μm), p-type Al (0.2) Ga (0.8) As buffer layer 8-11 (layer thickness 1 μm), p-type GaAs contact Layer 8-12 (layer thickness 0.2 μm).

  Each of these layers is formed by a crystal growth apparatus.

  Based on the above layer structure, a waveguide type APD is formed. The waveguide type APD has the structure shown in FIG.

  Hereinafter, a method for manufacturing the waveguide type APD according to this embodiment will be described.

  First, a first mesa having a length of 20 μm, a width of 4 μm, and a height of 4 to 5 μm is formed using wet etching or dry etching (RIE or the like). A second mesa having a height of about 2 to 3 μm is formed by wet or dry etching, leaving a region for forming an n-type contact electrode around the first mesa.

  In this case, the total mesa area of the first mesa and the second mesa is equal to the pn junction area, which is approximately 80 square μm.

  Next, a passivation film is formed using polyimide or a nitride film.

  Next, contact electrodes are formed on the upper surface of the p-type contact layer and the mesa upper surface where the n-type layer is exposed.

  A contact electrode made of Ti / Pt / Au is formed so as to cover the n electrode and the p electrode. The n electrode and the p electrode have a shape in which a coplanar line or a microstrip line or a combination of both is connected.

  In this case, an electrode constituting a ground is formed on the back surface of the substrate on which the element is formed.

  When the characteristics of this device were evaluated, the breakdown voltage was 10 V and the multiplication dark current was 0.1 μA.

  The quantum efficiency has wavelength dependence, but a maximum of 50% was obtained. The wavelength that can be received was in the region of 0.8 μm or less. The maximum response frequency was 36 GHz with a 50Ω load, and the GB product obtained a maximum of 330 GHz. In particular, the frequency response at a multiplication factor M = 2 to 8 was maintained at 36 GHz or more.

  An optical receiver is configured by connecting the semiconductor light receiving element according to the present embodiment to a preamplifier IC.

  When this optical receiver is used, it becomes possible to receive a high-speed modulated signal of 10 GHz or more with a wavelength of 0.4 μm to 0.8 μm with high sensitivity. This is effective, for example, as a light receiving element for communication using visible light or infrared light, which is used in optical communication using a plastic fiber.

  This example corresponds to the third embodiment.

  FIG. 9 is a diagram of a layer structure of a semiconductor light receiving element according to the fourth embodiment. The semiconductor light receiving element according to this embodiment is configured as an APD.

  The APD according to Example 4 includes an SI type indium phosphide (InP) substrate 9-1 and an n type InP buffer layer 9-2 (layer) formed on the SI type indium phosphide (InP) substrate 9-1 in this order. N-type InAlGaAs intermediate refractive index layer 9-3 (0.5 μm), n-type In (0.2) Al (0.8) As multiplication inhibiting layer 9-4 (layer thickness 0.05 μm) ), In (0.4) Al (0.6) As multiplication layer 9-5 (layer thickness 0.05 μm), and p-type In (0.2) Al (0.8) As multiplication inhibition layer The electric field relaxation layer 9-6 (layer thickness 0.05 μm), the p-type InAlGaAs field relaxation layer 9-7 (layer thickness 0.05 μm), and the first p-type InGaAs light absorption layer 9-8 (layer thickness 0.4 μm). ), A second p-type InGaAs light absorbing layer 9-9 (layer thickness 0.1 μm), and a p-type InAlGaAs intermediate refractive index layer 9-10. (Layer thickness 0.5 μm), p-type InP buffer layer 9-11 (layer thickness 2 μm), and p-type InGaAs contact layer 9-12 (layer thickness 0.5 μm).

  Each of these layers is formed using a crystal growth apparatus.

  In this embodiment, a waveguide type APD as shown in FIG. 7 for explaining the embodiment 2 is configured using this structure.

  Hereinafter, a method for manufacturing the waveguide type APD according to this embodiment will be described.

  First, a first mesa having a length of 10 μm, a width of 5 μm, and a height of 4 to 5 μm is formed using wet etching (such as a bromine system) or dry etching (such as RIE).

  A second mesa having a height of about 2 to 3 μm is formed using wet or dry etching, leaving a region for forming the n-type contact electrode adjacent to the first mesa and the long side.

  In this case, the total mesa area of the first mesa and the second mesa is equal to the pn junction area, which is approximately 50 square μm.

  Next, a passivation film is formed using polyimide or a nitride film.

  Next, contact electrodes are formed on the upper surface of the p-type contact layer and the mesa upper surface where the n-type layer is exposed.

  A contact electrode made of Ti / Pt / Au is formed so as to cover the n electrode and the p electrode. The n electrode and the p electrode have a shape in which a coplanar line or a microstrip line or a combination of both is connected.

  In this case, an electrode constituting a ground is formed on the back surface of the substrate on which the element is formed.

  In this case, an electrode constituting a ground is formed on the back surface of the substrate on which the element is formed.

  When the characteristics of this device were evaluated, the breakdown voltage was 12 V and the multiplication dark current was 0.5 μA. The quantum efficiency was 70%. The maximum response frequency was 40 GHz with a 50Ω load, and the GB product obtained a maximum of 250 GHz. In particular, the frequency response at a multiplication factor M = 2 to 5 was maintained at 40 GHz or higher.

  When the frequency characteristics were evaluated by connecting the waveguide type APD according to the present example and a preamplifier having a transformer impedance of 100Ω, a band of 40 GHz was obtained.

Further, when the receiver is configured using the waveguide type APD and the preamplifier according to the present embodiment and the reception sensitivity is evaluated at a bit rate of 40 Gb / s, the bit error rate is obtained when a 23-stage pseudo random signal is used. The light intensity giving (BER) 1 × 10 ⁻⁹ was −12 dBm. This is a high sensitivity optical receiver for 40 Gb / s.

  When this APD receiver is used, when configuring a 40 Gb / s transmission line, the amount of amplification of the optical preamplifier disposed in front of the APD receiver can be reduced, and an optical receiver with low power consumption can be configured. It is.

  Further, when the transmission distance is within 1 to 10 km, the transmission loss is estimated to be within 0.2 to 5 dBm. Therefore, by setting the transmission light output to about 0 to 3 dBm, an optical receiver in which the optical amplifier is omitted. This makes it possible to receive an optical signal.

It is explanatory drawing which shows the layer structure in the semiconductor photodetector which concerns on the 1st Embodiment of this invention. It is a graph which shows the composition of In (x) Al (1-x) As applicable to a multiplication layer. It is explanatory drawing which shows the structure (FIG. 3 (A)) of the semiconductor light receiving element which concerns on the 2nd Embodiment of this invention, and the structure (FIG. 3 (B)) of the conventional semiconductor light receiving element. 6 is an explanatory diagram illustrating a layer structure of a semiconductor light receiving element according to Example 1. FIG. 1 is a cross-sectional view illustrating a structure of a semiconductor light receiving element according to Example 1. FIG. 6 is an explanatory diagram showing a layer structure of a semiconductor light receiving element according to Example 2. FIG. 6 is a cross-sectional view illustrating a structure of a semiconductor light receiving element according to Example 2. FIG. 6 is a cross-sectional view illustrating a structure of a semiconductor light receiving element according to Example 3. FIG. 6 is a cross-sectional view illustrating a structure of a semiconductor light receiving element according to Example 4. FIG. It is explanatory drawing which shows the layer structure of the conventional SAM type | mold APD. It is the schematic which shows the structure of the conventional APD receiver. It is a block diagram of the conventional optical receiver using an optical preamplifier. It is explanatory drawing of the electric field distribution of the conventional SAM type | mold APD.

Explanation of symbols

1-1 Semiconductor substrate 1-2 n-type buffer layer 1-3 thin film multiplication layer 1-4 electric field relaxation layer 1-5 p-type light absorption layer 1
1-6 p-type light absorption layer 2
1-7 p-type buffer layer 1-8 p-type contact layer 2-1 (1-x) = − 0.3 log 10 (dm) +0.18
2-2 InAlAs composition range applicable as a thin film multiplication layer 3-01 p-type contact layer 3-02 p-type buffer layer 3-03 p ⁺ light absorption layer 3-04 p ^- light absorption layer 3-05 Electric field relaxation Layer 3-06 multiplication layer 3-07 n-type buffer layer 3-08 substrate 3-09 p-type contact layer 3-10 p-type buffer layer 3-11 p ⁺ type light absorption layer 3-12 p ^- type light absorption layer 3-13 Electric field relaxation layer 3-14 Multiplication suppression layer 3-15 Multiplication layer 3-16 Multiplication suppression layer 3-17 n-type buffer layer 3-18 substrate 4-1 n-type InP substrate 4-2 n-type InP Buffer layer 4-3 n-type InAlAs buffer layer 4-4 n-type In (0.4) Al (0.6) As buffer layer 4-5 In (0.4) Al (0.6) As multiplication layer 4 -6 1st p-type In (0.4) Al (0.6) As electric field relaxation layer 4-7 2p type InAlGaAs electric field relaxation layer 4-8 first p type InGaAs light absorption layer 4-9 second p type InGaAs light absorption layer 4-10 p type InP layer 4-11 p type InGaAs contact layer 5-1 signal light 5-2 reflection Prevention film 5-3 InP substrate 5-4 APD layer structure 5-5 n-type contact electrode 5-6 p-type contact electrode 5-7 p-electrode 5-8 n-electrode 6-1 SI-type InP substrate 6-2 n-type InP Buffer layer 6-3 n-type InAlGaAs intermediate refractive index layer 6-4 n-type In (0.4) Al (0.6) As buffer layer 6-5 In (0.4) Al (0.6) As multiplication Layer 6-6 First p-type In (0.4) Al (0.6) As electric field relaxation layer 6-7 Second p-type InAlGaAs electric field relaxation layer 6-8 First p-type InGaAs light absorption layer 6-9 Second p-type InGaAs Light absorption layer -10 p-type InAlGaAs intermediate refractive index layer 6-11 p-type InP buffer layer 6-12 p-type InGaAs contact layer 7-1 signal light 7-2 APD mesa 7-3 n-electrode mesa 7-4 n-electrode 7-5 p Electrode 7-6 Antireflection film 8-1 GaAs substrate 8-2 n-type Al (0.2) Ga (0.8) As buffer layer 8-3 n-type Al (0.12) Ga (0.88) As Intermediate refractive index layer 8-4 AlAs multiplication inhibiting layer 8-5 Al (0.2) Ga (0.8) As multiplication layer 8-6 AlAs multiplication inhibiting layer 8-7 p-type Al (0.2) Ga (0.8) As electric field relaxation layer 8-8 1st p-type In (0.1) Ga (0.9) As light absorption layer 8-9 2nd p-type In (0.1) Ga (0.9) As light absorption layer 8-10 p-type Al (0.12) Ga (0.88) As intermediate refractive index layer 8-11 p-type A l (0.2) Ga (0.8) As buffer layer 8-12 p-type GaAs contact layer 9-1 SI type InP substrate 9-2 n-type InP buffer layer 9-3 n-type InAlGaAs intermediate refractive index layer 9- 4 n-type In (0.2) Al (0.8) As multiplication inhibiting layer 9-5 In (0.4) Al (0.6) As multiplication layer 9-6 p-type In (0.2) Al (0.8) As multiplication suppression layer 9-7 p-type InAlGaAs electric field relaxation layer 9-8 first p-type InGaAs light absorption layer 9-9 second p-type InGaAs light absorption layer 9-10 p-type InAlGaAs intermediate refractive index layer 9-11 p-type InP buffer layer 9-12 p-type InGaAs contact layer 10-1 semiconductor substrate 10-2 n-type buffer layer 10-3 multiplication layer 10-4 electric field relaxation layer 10-5 first p-type light absorption layer 10 -6 2nd p-type light absorption layer 10- p-type buffer layer 10-8 p-type contact layer 11 - optical fiber 11-2 lens 11-3 APD
11-4 Preamplifier 11-5 MSL
11-6 High Frequency Connector 11-7 Terminal 12-1 Optical Fiber 12-2 Optical Signal 12-3 Optical Preamplifier 12-4 PIN-PD Optical Receiver 12-5 Electrical Signal 12-6 Optical Receiver Configured with Optical Preamplifier 13-1 p ⁺ layer 13-2 light absorption layer 13-3 electric field relaxation layer 13-4 multiplication layer 13-5 n ⁺ layer 13-6 effective multiplication layer width

Claims (14)

A substrate,
A multiplication layer formed on the substrate;
A multiplication inhibiting layer formed on both sides of the multiplication layer,
The semiconductor light-receiving element, wherein the multiplication inhibiting layer prevents an effective multiplication layer thickness from spreading with respect to a multiplication layer of less than 0.1 μm. The semiconductor light receiving element according to claim 1, wherein the substrate is an indium phosphide (InP) substrate. 3. The semiconductor light receiving element according to claim 2, wherein the multiplication inhibiting layer is made of In (x) Al (1-x) As (x ≦ 0.4). 4. The semiconductor light receiving element according to claim 3, wherein the multiplication suppression layer is made of a material having a larger band gap than the multiplication layer. 5. The semiconductor light-receiving element according to claim 2, wherein In (x) Al (1-x) As (0 ≦ x <0.52) is used as a material of the multiplication layer. . 6. The semiconductor light receiving element according to claim 5 , wherein the value of x in In (x) Al (1-x) As (0 ≦ x <0.52) is determined according to the following equation.
(1-x) ≧ k ₁ log 10 (dm) + k ₂
However, k ₁ is an arbitrary value satisfying k ₁ ≦ −0.3, and k ₂ is determined so that the curve of the above equation passes through the point (dm = 0.1, x = 0.52). Shall. The semiconductor light receiving element according to claim 1, wherein the substrate is a GaAs substrate. The semiconductor light receiving device according to any one of claims 1 to 7 wherein the multiplication preventing layer is characterized by is made of AlAs. The semiconductor light receiving device according to any one of claims 1 to 8 wherein the multiplication preventing layer may be equal to those having a thickness of 0.1μm or more 0.02 [mu] m. The semiconductor light receiving device according to any one of claims 1 to 9, wherein the multiplication preventing layer is characterized by having an impurity concentration of not less than 1 × 10 ¹⁷ cm ^-3. 11. The semiconductor light receiving element according to claim 1, wherein a layer thickness of the multiplication layer is 0.01 μm or more and less than 0.1 μm.   An optical receiver comprising: the semiconductor light receiving element according to claim 1; and a preamplifier IC connected to the semiconductor light receiving element. 12. A semiconductor light-receiving element according to claim 1 and a preamplifier IC connected to the semiconductor light-receiving element, wherein the light intensity giving a bit error rate (BER) of 1 × 10 ⁻⁹ is −26 dBm. An APD optical receiver for 10 Gb / s communication having the following reception sensitivity. 12. A semiconductor light receiving element according to claim 1, and a preamplifier IC connected to the semiconductor light receiving element, wherein the light intensity giving a bit error rate (BER) of 1 × 10 ⁻⁹ is −7 dBm. A 40 Gb / s communication APD receiver having the following reception sensitivity.

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