JP3156682B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having an excellent carrier confinement effect, for example, having a high luminous efficiency, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In order to reduce the cost of a subscriber semiconductor laser, a laser which does not require a temperature control device and has high luminous efficiency even at a high temperature is required. In order to improve the luminous efficiency at high temperature, in the multiple quantum well structure in the active region,
Select a material with a large internal quantum efficiency for the quantum well layer and a material with a large conduction band energy difference between the quantum well layer and the quantum well layer in order to confine electrons in the well layer. Is effective.

As such a material system, In (indium) As (arsenic) P
(Phosphorus) for the quantum well layer and InGa (carbonium) Al (aluminum) As for the barrier
The example of the semiconductor laser used for the layer is the 45th response by Yamada et al.
Preliminary Lectures for the Alliance for Physical Physics in Japan 30p-ZH-9
It has been announced. The structure will be described below according to the manufacturing method.
FIG. 3 is a structural diagram, and FIG. 4 is a process flow diagram.
As shown in FIG. 4, a 1.5 μm thick
N-InP lower cladding layer 12, 1150 i-In_0.52A
l_0.48As Lower SCH (Separate Confinement Heterostruc
100) i-InAs layer 13 and active region 14_0.45
P_0.55Well layer 15 and 100 i-In_0.52Al _0.16Ga_0.31As obstacle
I-In of wall layers 16 and 2050_0.52Al_0.48As upper SCH layer 1
7, p-InP upper cladding layer 18 having a thickness of 1 μm, p-InGaA
The s electrode contact layer 19 is sequentially grown, and
The plate 20 is manufactured. Here, the V-group is supplied by gas.
Substrate temperature 52 using a source molecular beam epitaxy apparatus
Prepared at 0 ° C.

[0004] Thereafter, the mesa stripe 21 is formed by etching into an inverted mesa shape in which the upper part of the mesa has a width of 4 µm and the lower part of the mesa has a width of 2.5 µm. At this time, the etching depth is p-InP
The upper SCH layer 17 of the i-In _0.52 Al _0.48 As is not exposed until the upper clad layer 18 is reached. Thereafter, an insulating film 22 made of SiO ₂ is formed on the entire surface of the semiconductor laser substrate 20, and a stripe-shaped hole 23 is formed in the insulating film above the mesa to secure conduction, and then a p-type ohmic electrode 24 is formed. Further, after the semiconductor laser substrate 20 is polished to a thickness of about 100 μm, an n-type ohmic electrode 25 is formed on the back surface and cleaved to an appropriate length to complete the semiconductor laser.

FIG. 3 shows a current path when a current is injected into the semiconductor laser 26. In addition to the current 29 flowing into the active region 14, there is a leakage current 28 spreading in the lateral direction.

[0006]

The semiconductor laser as described above has a problem that the current spreads in the horizontal direction below the mesa and becomes a leakage current 28, so that the oscillation threshold current increases and the luminous efficiency decreases. there were. In order to eliminate such a leakage current, a method of regrowing the current block layer after the mesa etching is usually employed. However, regrowth also has the following problems. In the present material system, the group V constituting the substrate semiconductor material is phosphorus, and the group V constituting the semiconductor material in the active region is different from arsenic. For example, when a group V gas introduced at the time of temperature rise for regrowth is arsine,
At a high temperature of 400 ° C. or higher, V group substitution occurred, and good regrowth such as clouding of the substrate was impossible. When phosphine is used as the group V gas introduced at the time of temperature rise before regrowth, arsenic is replaced by phosphorus in the exposed portion of the active region. There is also a problem that the crystallinity is degraded as the substitution proceeds, and the luminous efficiency is reduced. In addition, since the layer containing Al is once exposed to the atmosphere, there are many non-radiative recombination centers due to Al oxide in the active region, which causes a problem that the luminous efficiency is reduced. Even if the wide gap semiconductor layer for trapping carriers and light is regrown outside the active region, the non-radiative recombination center exists inside the wide gap semiconductor layer, so the non-radiative recombination center exists. The influence of the center could not be removed, and this was a factor in lowering the luminous efficiency.

The present invention has been made in view of the above-mentioned problems, and has as its object to provide a semiconductor device having high luminous efficiency and a method of manufacturing the same.

[0008]

The present invention has the following features to attain the object mentioned above. That is, the semiconductor device according to claim 1 has an active region containing arsenic,
In the semiconductor element whose side surface is exposed or covered with the regrown layer, a wide gap semiconductor layer having a thickness equal to or more than the de Broglie wavelength and equal to or less than the critical strain thickness exists on the side surface of the active region. It is characterized by the following.

In the semiconductor device according to the second aspect, the first aspect is as follows.
The semiconductor device according to claim 1, wherein a mesa portion including the active region is formed, and the wide gap semiconductor layer is formed from a side surface of the active region to an inside of the mesa portion.

According to a third aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: forming a lower cladding layer on a semiconductor substrate using a crystal growing apparatus; and forming an active region containing arsenic on the lower cladding layer. Forming a semiconductor device substrate by forming an upper cladding layer on the active region, and forming a cap layer on the upper cladding layer, and then etching the semiconductor device substrate in a mesa shape. The method of manufacturing a semiconductor device, further comprising a step of, after raising the temperature of the semiconductor device substrate with the side surfaces of the active region exposed to 650 ° C., introducing 1 × 10 ⁻⁵ mol / cm ^{2 of} phosphine. I do.

According to a fourth aspect of the present invention, in the method of manufacturing a semiconductor device according to the third aspect, the substrate temperature is set to 400 ° C. before regrowth after the step of etching the semiconductor element substrate into a mesa. , And a step of raising the temperature in a hydrogen or nitrogen atmosphere up to about 400 ° C. to 650 ° C.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a semiconductor device and a method of manufacturing the same according to the present invention will be described below with reference to FIGS. FIG. 1 is a structural view of the present device, and FIG. 2 is a process flow diagram of the present device. The structure will be described below according to the manufacturing method.

As shown in FIG. 2A, the InP substrate 1
1, 1.5 μm thick n-InP lower cladding layer 1
2. 1150 i-In _0.52 Al _0.48 As lower SCH layer 13, 100 i-InAs _0.45 P _0.55 well layer 15 as active region 14
When 100 of the _{i-In 0.52 Al 0.16 Ga 0.} 31 As barrier layer 16,2050
The i-In _0.52 Al _0.48 As upper SCH layer 17 and the 1 μm-thick p-InP upper cladding layer 18 were sequentially grown to produce a semiconductor laser substrate 41. Here, the substrate was manufactured at a substrate temperature of 520 ° C. by using a gas source molecular beam epitaxy apparatus that supplies the group V with a gas.

Thereafter, using the SiO ₂ film 42 as a mask, a mesa stripe 43 was formed by etching in a stripe shape so that the mesa width was about 2 μm. At this time, the etching depth was set to reach the InP substrate 11. ((B) of FIG. 2) After removing the SiO ₂ film 42, it was put into the crystal growth apparatus again. This apparatus was an organometallic vapor phase epitaxy apparatus. The procedure for raising the temperature before crystal growth was as follows.

As shown in FIG. 2B, in the initial state, the oxide layer 54 is formed thicker in the portion where the Al atoms exist on the side surface of the mesa than in the InP surface such as the bottom surface portion 51 of the substrate. ing. In this state, first, arsine was introduced and the temperature was raised. After the substrate temperature reached 400 ° C., the device was kept on standby for 2 hours while maintaining the temperature. During this waiting process, the oxide layer 54
Desorption of about 0% has been observed in another experiment. Also, at this temperature, the degree of V group substitution was very small, and the introduction of arsine did not cause roughness of the InP substrate 11 portion.

Further, the temperature was raised in a hydrogen or nitrogen atmosphere until the temperature reached 650 ° C. while blocking arsine. At this stage, phosphorus and arsenic atoms on the substrate surface are desorbed, and III
The surface was a stable state, and the substrate and the mesa side surface were not roughened during the heating time. After the substrate temperature reached 650 ° C., phosphine was introduced at a flow rate of 100 SCCM for 10 seconds. This flow rate is about 1 × 10 ⁻⁵ mol / cm ² as the PH ₃ amount supplied onto the substrate in the present apparatus.

By the introduction of the phosphine, phosphorus atoms are supplied to the crystal surface which has been in the group III plane, and the substrate is formed in a normal state.
I-In _0.52 Al _0.48 As lower SCH layer 13 near the active region, i-In _0.52 Al _0.48 As upper SCH layer 1 near the active region
7, an i-InAs _{0. 45} P _0.55 well layers 15 of the active region 14 i-
In the portion such as the In _0.52 Al _0.16 Ga _0.31 As barrier layer 16, part of the V group is replaced with phosphorus from the surface to a depth of about 4-5 monolayers, and as shown in FIG. A replacement region 58 was formed. Such a state of group V substitution is reported by Kurihara et al. In IEICE Technical Report LQE 98-24, p. 55.

In a material system such as InAlAs, InAlGaAs, InAsP, etc., when phosphorus is mixed into the group V, the forbidden band width is widened to form a wide gap semiconductor layer, and the refractive index is lowered.
Since this wide gap semiconductor layer can be formed inside the non-radiative recombination center existing on the side surface of the mesa, the laser light in the active region is strongly bound to the inside of the mesa,
The effect of non-radiative recombination centers 59 caused by Al oxide remaining on the mesa side surface is reduced. When a wide-gap semiconductor is present also for a carrier, if the thickness of the wide-gap semiconductor layer is greater than the de Broglie wavelength, there is almost no leakage of the carrier to the outside of the wide-gap semiconductor layer. The non-radiative recombination centers 59 that are trapped outside are reduced in ineffective carriers, and carrier injection effectively contributes to light emission.

The arsenic / phosphorus-substituted region 58 of about 4 to 5 monolayers formed here is a strained layer, but does not have a defect or the like since the thickness is less than the critical thickness. Moreover,
The strained layer has a large bandgap bend, and effectively acts to confine carriers even though it is a thin layer.

Thereafter, the p-type InP buried layer 60 and the p-type InGaAs cap layer 61 are immediately
nm. ((D) of FIG. 2) After being taken out from the crystal growing apparatus, as shown in (e) of FIG.
After polishing the semiconductor laser substrate to a thickness of about 100 μm, the n-type ohmic electrode
Was formed and cleaved to an appropriate length to complete a semiconductor laser.

The oscillation threshold of the semiconductor laser of this embodiment is:
At room temperature, the current was 8 mA, which was almost halved compared to the conventional 15 mA. This effect is considered to be due to the fact that the effect of the non-radiative recombination center on the side surface of the mesa was reduced in addition to the reduction of the leakage current as the buried structure. In addition, the characteristic temperature was 120 K, which is the same as that of the conventional example. The reason why such temperature characteristics are good is that an Al-based material having a large conduction band energy difference is used for the barrier layer and the SCH layer in the active region.

In the above-described embodiment, arsine and phosphine are used as the group V material gas. However, these gases may be replaced with other raw materials such as tertiary butyl arsine and tertiary butyl phosphine which can be used for the same purpose. Similar effects can be obtained. Further, in this embodiment, the semiconductor laser is used. However, the present invention can be applied to other semiconductor elements such as an avalanche photodiode using InAlAs and a single electron tunnel transistor.

[0023]

According to the present invention, the following effects can be obtained. (1) According to the semiconductor device of the first aspect, since the wide gap semiconductor layer having a thickness not less than the de Broglie wavelength and not more than the critical strain thickness exists on the side surface of the active region, the thickness of the wide gap semiconductor layer is large. Since the thickness is more than the de Broglie wavelength, there is almost no carrier leakage up to the outside, so in the case of a semiconductor laser or the like, it is captured by the non-radiative recombination center outside the wide gap semiconductor layer. As a result, ineffective carriers are reduced, and carrier injection can be effectively contributed to light emission. Further, although the wide gap semiconductor layer is a strained layer, since the thickness is equal to or less than the critical film thickness, defects and the like do not occur, and since the strained layer has a large band gap, it is a thin layer. It can effectively act on the confinement of the carrier.

(2) According to the semiconductor device of the second aspect, the mesa portion including the active region is formed, and the wide gap semiconductor layer is formed from the side surface of the active region to the inside of the mesa portion. In the case of a laser or the like, since the wide gap semiconductor layer can be formed inside the non-radiative recombination center existing on the side surface of the mesa portion, the laser light in the active region is more strongly trapped inside the mesa portion, and the mesa portion It is possible to reduce the influence of non-radiative recombination centers generated by, for example, Al oxide remaining on the side surface.

(3) According to the method of manufacturing a semiconductor device according to the third aspect, after the temperature of the semiconductor device substrate in which the side surface of the active region is exposed is raised to 650 ° C., phosphine is reduced to 1 × 10 5
^-5 mol / cm ^{2 is} introduced.By introducing phosphine at a high temperature, the group V atoms constituting the active layer material are replaced by phosphorus and the composition becomes wide-gap. The effect of non-radiative recombination centers can be significantly reduced.

(4) According to the method of manufacturing a semiconductor device according to the fourth aspect, before regrowth after the step of etching the semiconductor device substrate into a mesa shape, the substrate temperature is increased in an arsine atmosphere until the substrate temperature reaches 400 ° C. Since the oxide film is desorbed at a low temperature in an arsine atmosphere, the oxide film can be effectively removed and the luminous efficiency can be improved.
Since the step of raising the temperature in a hydrogen or nitrogen atmosphere from 00 ° C. to 650 ° C. is included, it is possible to suppress both the roughness of the substrate and the decrease in the luminous efficiency of the active region. From the above points, for example, a semiconductor laser having good long-wavelength luminous efficiency and good temperature characteristics can be realized.

[Brief description of the drawings]

FIG. 1 is a structural diagram showing one embodiment of a semiconductor device according to the present invention.

FIG. 2 is a process flow chart showing one embodiment of a semiconductor device according to the present invention.

FIG. 3 is a structural diagram showing a conventional example of a semiconductor device according to the present invention.

FIG. 4 is a process flow chart showing a conventional example of a semiconductor device according to the present invention.

[Explanation of symbols]

Reference Signs List 11 InP substrate 12 n-InP lower cladding layer 13 i-In _0.52 Al _0.48 As lower SCH layer 14 active region 15 i-InAs _0.45 P _0.55 well layer 16 i-In _0.52 Al _0.16 Ga _0.31 As barrier layer 17 i-In _0.52 Al _0.48 As upper SCH layer 18 p-InP upper cladding layer 19 p-InGaAs electrode contact layer 20 semiconductor laser substrate 21 mesa stripe 22 insulating film 23 striped hole 24 p-type ohmic electrode 25 n-type ohmic electrode 28 leakage current 29 activity Current flowing into region 41 Semiconductor laser substrate 42 SiO ₂ film 43 Mesa stripe 51 Substrate bottom surface 54 Oxide layer 58 Arsenic / phosphorus substitution region 59 Non-emission center 60 p-type InP buried layer 61 p-type InGaAs cap layer 62 p-type ohmic electrode 63 n-type ohmic electrode

Claims (4)

(57) [Claims] 1. A semiconductor device having an active region containing arsenic, the side surface of which is exposed or covered with a regrown layer, wherein the side surface of the active region has a de Broglie wavelength or more and a strain critical A semiconductor device comprising a wide gap semiconductor layer having a thickness equal to or less than a film thickness. 2. The semiconductor device according to claim 1, wherein a mesa portion including the active region is formed, and the wide gap semiconductor layer is formed from a side surface of the active region to an inside of the mesa portion. Characteristic semiconductor element. 3. A step of forming a lower cladding layer on a semiconductor substrate using a crystal growing apparatus, a step of forming an active region containing arsenic on the lower cladding layer, and forming an upper cladding layer on the active region. A method of manufacturing a semiconductor device, comprising: forming a semiconductor device substrate by a manufacturing process and a process of forming a cap layer on the upper clad layer; and then etching the semiconductor device substrate in a mesa shape. After the temperature of the semiconductor element substrate with the side surfaces exposed was raised to 650 ° C., phosphine was added at 1 × 10 ⁻⁵ mo.
A method for manufacturing a semiconductor device, comprising a step of introducing l / cm ² . 4. The method of manufacturing a semiconductor device according to claim 3, wherein the temperature is increased in an arsine atmosphere until the substrate temperature reaches 400 ° C. before regrowth after the step of etching the semiconductor device substrate into a mesa. A method for manufacturing a semiconductor device, comprising: a step of raising the temperature in a hydrogen or nitrogen atmosphere from 400 ° C. to about 650 ° C.