JP2616532B2 - Semiconductor laser and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high performance semiconductor laser required for optical fiber communication and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in order to improve the characteristics of a semiconductor laser, a single quantum well (SQW) laser or a multiple quantum well (MQ) having an active layer of a semiconductor laser in a quantum well structure has been used.
QW) Research on lasers has been conducted. The semiconductor laser having the quantum well active layer can be expected to have good characteristics that are not available in the ordinary bulk type active layer due to the quantum size effect. For example, high efficiency and large output operation can be achieved at a low threshold value by increasing the differential gain and reducing TM emission, etc., and high-speed response and low chirping can be obtained by increasing the relaxation oscillation frequency and decreasing the line width increase coefficient. .

However, in order to further increase the differential gain, the application of a modulation-doped MQW structure for doping a barrier layer of a quantum well is being studied in addition to the use of a strained quantum well and a reduction in the thickness of a barrier layer. .Wolmi, Tea, Mishima, N. Chinone, Shahjan Journal Affiliate Physics, 51 (199
0) 88 (K. Uomi, T. Mishima, N. Chinone, Jpn. J. App
l.Phys., 51 (1990) 88)].

FIG. 8 shows an example of a conventional semiconductor laser. 3
1 n-GaAs substrate, 32 is n-GaAs buffer layer 33 is n-In _0.6 Al _0.4 As cladding layer, an undoped AlGaAs optical confinement layer 34, an undoped GaAs well layers 35, 36 an undoped Ga _0.8 Al _0.2 A
s layer, 37 is Be-doped Ga _0.8 Al _0.2 As, 38 is a modulation-doped quantum well layer, 39 is a p-AlGaAs cladding layer, 40 is an n-GaAs current constriction layer, 41 is SiO ₂
An insulating layer, 42 is a Zn diffusion region, 43 is a p-side electrode made of Au / Cr, and 44 is an n-side electrode made of AuGeNi.

FIG. 9 shows the structure of the modulation-doped quantum well layer shown in FIG.
As shown in (b), an undoped GaAs well layer 35, an undoped GaAlAs barrier layer 36 and a modulation doped layer 37
And a barrier layer composed of

In the conventional modulation-doped quantum well semiconductor laser device configured as described above, a current is applied to the p-side electrode 4.
3, and injected into the modulation-doped quantum well layer 38 after being sandwiched by the Zn diffusion region 42. An increase in the relaxation oscillation frequency that increases with an increase in the differential gain was confirmed in the modulation-doped quantum well structure shown in FIG. 8 with respect to the undoped quantum well structure.

[0007]

As described above, the modulation-doped quantum well layer 38 of the semiconductor laser having the modulation-doped quantum well structure shown in FIG. 8 has the undoped GaAs well layer 35 as described above. Undoped AlGaAs barrier layer 36 and Be-doped AlGaAs modulation doped layer 37
And a barrier layer comprising:

A comparison of the relaxation oscillation frequency between this semiconductor laser and a semiconductor laser having a uniformly doped quantum well structure in which a well layer and a barrier layer are uniformly doped as shown in FIG. Only an equal increase in the relaxation oscillation frequency was confirmed as compared to the quantum well semiconductor laser. This is presumably because the modulation doping structure shown in FIG. 9B or 9C was diffused by the subsequent heat treatment step, and the modulation doping structure disappeared, resulting in a uniform doping structure. This is shown in FIG. In the modulation-doped quantum well structure having the structure shown in FIG. 4B, the concentration of Be was increased only in the modulation-doped layer before the heat treatment, but after the heat treatment, Be diffused from the modulation-doped layer. It is uniform.
As a result, it is considered that there is no difference between the laser having the uniform doping structure and the laser having the modulation doping structure. This is because the elements used for doping diffuse at high temperatures.

In view of the above problems, the present invention suppresses the diffusion of a dopant element in a modulation-doped quantum well layer having a modulation-doped structure by performing modulation doping, thereby suppressing the destruction of the modulation-doped structure, and reducing the cladding layer. An object of the present invention is to provide a semiconductor laser having a structure that suppresses diffusion of a dopant into a modulation-doped quantum well layer and suppresses destruction of a modulation doping structure of the modulation-doped quantum well layer.

[0010]

Means for Solving the Problems A semiconductor laser of the present invention in order to achieve the object, a base plate, first on the substrate
A waveguide layer of a conduction type , a well layer and a barrier layer alternately stacked, and a modulation-doped quantum well layer modulated and doped in the barrier layer; a stop layer for stopping diffusion of the dopant; And a cladding layer are sequentially stacked, and the energy gap of the waveguide layer is
Or less of the energy gap, the well layer is, before Symbol
Smaller energy gap than the guiding Namijiso, the barrier layer is in the middle of the energy gap of the prior Kishirube waveguide layer and the well layer comprises a modulation doped layer having electrical Den to a portion,
The energy gap of the stop layer depends on the barrier layer.
, And a crystal in which a dopant is added below its solid solubility limit .

Further, on the base plate, the substrate following energy
Intermediate energy gap of growing a waveguide layer that having a first conductive heat transfer-type is over-gap, and the energy gap is smaller well layer than the previous Kishirube Namijiso, and the waveguide layer and the well layer An undoped first barrier layer;
Growing a modulation-doped quantum well layer in which a modulation-doped layer and an undoped second barrier layer are alternately stacked;
An energy gap is equal to or greater than the barrier layer, and a step of growing a stop layer for stopping diffusion of the dopant, the energy gap is equal to or greater than the stop layer,
A step of growing a cladding layer having a second conductivity type, an etching step of etching up to the substrate in a stripe shape, and forming a side surface of the stripe with a second conductivity type crystal and a first conductivity type crystal. Growing a crystal of the second conductivity type and embedding the stripe.

[0012]

In order to preserve the modulation doping structure, first, the concentration of the dopant added to the modulation doping layer needs to be lower than the saturation concentration of the dopant depending on the crystal composition.
However, even when the amount of the dopant in the modulation doping layer is equal to or lower than the saturation concentration, the modulation doping structure may disappear. This occurs when there is a layer to which a dopant having a saturation concentration or more is added near the modulation doping layer. Therefore, it is necessary to dispose a layer having a low saturation concentration away from the modulation doping layer and to reduce the amount of the dopant to the saturation concentration or less. In the present invention, the undoped layer is inserted between the cladding layer and the modulation doping layer even when the concentration of Zn in the cladding layer is set to be equal to or lower than the saturation concentration of Zn, or when the cladding layer is doped with Zn having a concentration close to the saturation concentration. This can prevent diffusion. However, at the time of manufacturing the laser structure, it is necessary to dope the waveguide layer. Therefore, instead of the dopant such as InP or the like having a low Zn saturation concentration, a layer of, for example, InGaAsP or the like is inserted, so that the modulation doping structure is obtained. Save is realized.

[0013]

EXAMPLES The following preliminary experiments were attempted to realize the following examples.

As shown in FIG. 14, the well layer has a thickness of 5n.
m, in a 10-pair modulation-doped MQW structure in which the barrier layer is 10 nm thick and the central 3 nm region is doped with Zn at 1 × 10 ¹⁸ cm ⁻³ , a p-type modulation cladding layer is usually formed after growing the modulation doping structure. 300n InP layer
grow m. The growth temperature was 620 degrees and the growth time was 90 minutes. After growth, the modulation doping structure was measured by SIMS, and it was confirmed that the modulation doping structure was preserved.

However, in order to obtain a PBH structure (buried laser structure), a liquid layer growth method (Liquid Phase) is used.
After burying and growing the current constriction layer with a pnp-InP layer by Epitaxy, the modulation dope structure was again measured by SIMS, and as a result, the modulation dope structure disappeared.

On the other hand, after growing the modulation doping structure, as shown in FIG. 10A, an undoped-InP layer is grown to 300 nm in place of the p-InP layer, and thereafter the p-InP is grown.
As a result of growing the P layer and measuring the modulation dope structure by SIMS, it was confirmed that the modulation dope structure was preserved.

From the results of FIG. 10, when the concentration of the InP layer grown after the growth of the modulation doping structure is 0 (case b), it can be seen from the result of FIG. As can be seen, the concentration of InP is 1 × 10 ¹⁸ c
In the case of m ⁻³ (in the case of c), the modulation doping structure has disappeared. Therefore, undoped In adjacent to the modulation doped layer
It can be seen that even if P can be grown, a doped p-InP crystal cannot be grown.

From the above experimental results, the modulation doping structure disappears when there is a doped p-InP layer near the modulation doping layer, but when the p-InP layer is not doped, the modulation doping structure becomes Has not changed at all. It is considered that the disappearance of the modulation dope structure is that Zn doped in the p-InP layer diffuses into the modulation dope layer as interstitial atoms Zni and destroys the modulation dope structure. Therefore, two methods are conceivable for preserving the modulation doping structure.

1. As shown in FIG. 3A, the doped p-InP layer 9 is placed at a position away from the modulation-doped quantum well layer 7, and the number of Zn interstitial atoms Zni diffused from the p-InP layer 9 is reduced. Lower. As shown in FIG. 3A, a p-InGaAsP layer 8 for stopping the diffusion of Zn was provided under the p-InP cladding layer 9. This, p
-InGaAsP layer 8 also functions as a second waveguide. Since the InGaAsP layer 8 has a high solid solubility limit of Zn,
Even if Zn diffuses from the cladding layer 9, this In
Zn stops in the GaAsP layer 8. Therefore, I
The nGaAsP layer 8 acts as a low resistance layer between the p-InP cladding layer 9 and the modulation doping layer 7 without generating Zn interstitial atoms Zni.

2. As shown in FIG. 3B, p-InP
The Zn concentration of the layer 9 is reduced. The amount of Zn that can be dissolved in the p-InP layer 9 depends on the crystal growth temperature and the total gas amount during the crystal growth, but is considered to be about 1 × 10 ¹⁸ cm ⁻³ . When a concentration near the solid solubility limit is used, a large amount of interstitial atoms Zni are generated. Therefore, the p-InP cladding layer 9 has 5 × 10
^It is necessary to dope about ¹⁷ cm ^-3 .

The above two means prevent the Zn element from diffusing into the modulation-doped quantum well layer from outside the layer. With this means alone, it is possible to prevent the doping element from diffusing into the modulation doping layer from outside the modulation doping layer, but prevent the element doped into the modulation doping layer itself from diffusing and destroying the modulation doping layer. It is not possible. Therefore, in addition to these means, FIG.
As shown in (a), the doping element (Z
It is necessary to prevent n) from diffusing and from the modulation doped layer to the outside. There are three ways to do this.

1. The modulation doping concentration of the p-InGaAsP modulation doping layer 5 is set to be lower than the solid solubility limit of the InGaAsP crystal. This is because, similarly to the p-InP cladding layer 9 described above, when Zn exceeding the solid solubility limit is doped, the modulation doping layer disappears due to interstitial atoms Zni generated in the modulation doping layer itself. FIG. 11 shows p-In
The concentration of Zn in the GaAsP modulation doped layer is 1 × 10 ¹⁸ cm
^{-3, 2 × 10 18 cm -3} , showing a change of a modulation doped structure as 5 × 10 ¹⁸ cm ^-3. As a result, the Zn concentration was set to 2 × 10
Below ¹⁸ cm ^-3 , the modulation doping structure is preserved, and Z
It has been found that the n concentration needs to be 2 × 10 ¹⁸ cm ⁻³ or less.

2. Since the p-InGaAsP modulation-doped layer 5 is modulation-doped, the concentration of Zn is large.
Zn tends to diffuse out of this layer. In order to prevent the diffusion of Zn, p-InGaAs is formed by the diffusion of Zn.
If the crystal energy of the sP modulation-doped layer is increased to be in an unstable state, diffusion of Zn should be able to be suppressed.

For example, when the lattice constant of the crystal of the layer to be subjected to modulation doping (modulation doping layer) is larger than the lattice constant of the adjacent barrier layer, the layer to be subjected to modulation doping generates a compressive strain and becomes unstable. Although the internal energy of the crystal increases, the lattice constant of the modulation doping layer decreases as the concentration of doped Zn increases.
, The compressive strain is reduced and the crystal becomes stable.

That is, if a compressive strain is given to the modulation doping layer in advance (the lattice constant of the modulation doping layer is made larger than that of the adjacent barrier layer), Zn
The diffusion of Zn causes a decrease in the Zn concentration, which leads to an increase in the energy of the crystal, so that the diffusion of Zn is suppressed. Therefore, by making the lattice constant of the modulation doped layer larger than the lattice constant of the adjacent barrier layer, the undoped-InGaAs
The diffusion of Zn into the sP layer was suppressed. In this case, the concentration of Zn added to the modulation doping layer could be increased to 5 × 10 ¹⁸ cm ⁻³ .

3. FIG. 4B shows the energy states of the well layer and the barrier layer of the modulation-doped quantum well layer. As shown in FIG. 4 (c), the InGaAsP crystal constituting the barrier layer
It is better to use a crystal composition that reduces the energy gap.
The saturation concentration of n increases. However, when the energy gap of the crystal of the barrier layer is reduced, the energy gap difference between the well layer and the barrier layer is reduced, and there is a problem that electrons supplied to the laser overflow from the well layer and the luminous efficiency is reduced. Therefore, the energy gap of the crystal of the modulation doping layer 5 in the barrier layer is not reduced, and only the composition of the undoped-InGaAsP layer 4 is reduced in energy gap, and instead, a crystal having a high Zn saturation concentration is used. In order to achieve this, Zn atoms diffused from the modulation doping layer 5 are not doped with the undoped-InGaAsP layer 4.
You can stop with That is, undoped
The composition of the InGaAsP layer 4 is changed to the modulation doping layer 5 of the barrier layer.
And the composition of the well layer 3, the solid solubility limit of Zn in the undoped-InGaAsP layer 4 is increased, and diffusion is suppressed. In this case, as shown in FIG. 13, the Zn concentration added to the modulation doping layer increased to 8 × 10 ¹⁸ cm ⁻³ .

The barrier layer may have a structure in which an undoped layer having a large energy gap is sandwiched between modulation modulation layers having a small energy gap. It was big.

Further, by making the energy gap of the modulation doped layer small and increasing the energy gap of the undoped layer, the Zn doping concentration can be increased in the structure in which the energy gap between the well layer and the barrier layer is increased.

Embodiment 1 A semiconductor laser according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a structural diagram of a strained quantum well semiconductor laser according to an embodiment of the present invention. 1 and 2, reference numeral 1 denotes an Sn-doped InP substrate, and 2 denotes n-InGa.
AsP waveguide layer, 3 is a 5 nm-thick InGaAs well layer, 4 is a 3.5-nm-thick undoped-InGaAsP layer.
5 and 3 are p-InGaAsP modulation doped layers having a thickness of 3 nm, and 6 are undoped InGaAsP layers having a thickness of 3.5 nm.
Layer, 7 is a modulation-doped quantum well layer having 10 wells, 8 is a p-InGaAsP layer having a thickness of 90 nm, 9 is a p-InP cladding layer (Zn = 7 × 10 ¹⁷ cm −3), and 10 is pn-
p current blocking layer, 11 is a mesa-shaped active layer region, 12
Is an n-side electrode made of Au / Sn, and 13 is a p-side electrode made of Au / Zn. FIG. 2 shows a detailed view of the modulation-doped quantum well layer and its energy state diagram. As shown in FIG. 2, the modulation-doped quantum well layer 7 is composed of an InGaAs well layer 3, an undoped InGaAsP layer and a p-InGa layer.
It is made of a barrier layer composed of an AsP modulation doped layer.

The operation of the structure of the semiconductor laser of this embodiment having the above-described structure will be described below with reference to FIG. The current introduced from the p-side electrode 13 is injected into the modulation-doped quantum well 7 after being narrowed by the current blocking layer 10.

The modulation doping layer 5 contains 2 × 10 ¹⁸ cm of Zn.
^{-3 is} doped. As shown in FIG. 11, the doping amount is such that the modulation doping layer 5 is not destroyed.

The thickness of the well layer depends on the composition of the well layer.
The wavelength was set to 5 nm so as to obtain an emission wavelength of 55 μm.
In the first embodiment, the p-InGaAsP layer 8 is stacked between the p-InP cladding layer 9 and the modulation-doped quantum well layer 7 to suppress the diffusion of Zn from the p-InP cladding layer 9; Interstitial atoms Z in the p-InGaAsP layer 8
It was confirmed that the ni concentration was attenuated and the Zn profile of the modulation doped layer in the modulation doped quantum well layer 7 was preserved.

Actually, as a result of fabricating the laser shown in this embodiment and evaluating various characteristics, the relaxation oscillation frequency was 10 GHz /
mW, which is 1.7 times higher than 6 GHz / mW when the modulation doping is not performed in the same structure. this is,
It is considered that the differential gain increases due to the adaptation of the modulation doping structure.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 5 is a structural view of a strained quantum well semiconductor laser according to a second embodiment of the present invention. The composition of the p-InGaAsP modulation doped layer 5 in FIG.
In0.76Ga0.24As0.61P
0.39 strain modulation doping layer 14. Thereby, the strain modulation doping layer 14 was further set to a modulation doping concentration of 5 × 10 ¹⁸ cm ^-3 from the adjacent barrier layer. As shown in FIG. 11, the doping amount destroys the modulation doping layer. However, as in the present embodiment, the modulation doping layer is formed into a strain modulation doping layer 14 in which a compression strain is applied, so that the doping concentration is reduced. The modulation doping layer was not destroyed even if was increased.

In the structure of the semiconductor laser according to the present embodiment configured as described above, the concentration of Zn can be increased to 2.5 times that of the first embodiment because the diffusion of Zn in the modulation doped layer is suppressed. As a result, the relaxation oscillation frequency f _r is further improved and 13 GHz.

Embodiment 3 Hereinafter, a third embodiment of the present invention will be described with reference to the drawings.

FIG. 6 is a structural view of a strained quantum well semiconductor laser according to a second embodiment of the present invention. The step-type barrier layer 15 in which the composition of the undoped-InGaAsP layer 4 adjacent to the p-InGaAsP strain modulation doped layer 14 in FIG. 5 is intermediate between the composition of the modulation doped layer and the composition of the well layer.
By doing so, the solid solubility limit of Zn in the undoped-InGaAsP layer increases, and diffusion is suppressed. The modulation doping concentration was 8 × 10 ¹⁸ cm ⁻³ . This doping amount is also shown in FIG.
The layer adjacent to the modulation doped layer 5 is larger than the concentration at which the modulation doped layer is not destroyed as shown in FIG.
By doing so, the amount of doping in the modulation doping layer could be increased.

In the structure of the semiconductor laser of this embodiment configured as described above, the concentration of Zn can be four times that of the first embodiment because the diffusion of Zn in the modulation doped layer is suppressed. As a result, the relaxation oscillation frequency f _r is further improved and 15 GHz.

(Embodiment 4) FIG. 4 shows a method of manufacturing a semiconductor laser according to an embodiment of the present invention.

A 60 nm-thick n-InGaAsP waveguide layer 2 is formed on a Sn-doped InP substrate 1 by MOVPE.
Grow. Next, a 5 nm-thick InGaAs well layer 3, a 3.5 nm-thick undoped-InGaAsP barrier layer 4, a 3 nm-thick p-InGaAsP modulation doped layer 5, and a 3.5 nm-thick undoped-InGaAsP barrier layer 6 are formed. As one pair, the well layer 3 and the barrier layers 4 to 6 composed of three layers are repeatedly grown to form the modulation-doped quantum well layer 7 having 10 pairs.

Further, p-InGa is used as a Zn stop layer.
AsP layer 8 (Zn = 5 × 10¹⁷cm ^-3), P-InP
Rad layer 9 (Zn = 5 × 10¹⁷cm^-3) Continuously grow
Then, a crystal growth step (FIG. 7A) is performed.

Next, from the p-InP cladding layer 9 to the n-
A mesa etching step of etching the InGaAsP waveguide layer 2 into a mesa shape 11 (FIG. 7B).

Then, p-InP, n-InP, p-In
A buried growth step for LPE growth of the P current block layer 10 (FIG. 7C).

Finally, an electrode deposition step (FIG. 7D) for forming the n-side electrode 12 and the p-side electrode 13 by vapor deposition is performed to obtain a laser structure.

The determination of the Zn concentration of the modulation doping layer 5 and the p-InP layer 9 of the semiconductor laser manufactured as described above according to this embodiment will be described below.

As a result of obtaining the relationship between the flow rate of DMZn (dimethyl Zn) and the hole concentration, the result shown in FIG. 12 was obtained. Here, the hole concentration of InP is saturated at 9 × 10 ¹⁷ cm ⁻³ , and the hole concentration of InGaAsP is saturated at 5 × 10 ¹⁸ cm ⁻³ . Therefore, the concentration of Zn to be doped into InP is 5 × 10 ¹⁷ cm ⁻³ , which is の of the saturation concentration.
The concentration of Zn doped into aAsP is 3 × 10 ¹⁸ c
m ^-3 . Total flow rate is 5 L / min, growth temperature is 640
° C.

The semiconductor laser of the first embodiment is realized by the method of manufacturing a semiconductor laser described above.

The manufacturing method of the semiconductor laser shown in the second and third embodiments is almost the same as the manufacturing method of the first embodiment. The difference is that in the second embodiment, the InGaAsP strain modulation doping layer 14 is grown as a modulation doping layer, and in the third embodiment, the undoped barrier layer is grown as an undoped InGaAsP step-type barrier layer. .

In the above embodiment, a crystal of an InP-based compound semiconductor was used.
System, GaAs system, ZnSeS system, InAlAs system, Al
A semiconductor material such as a GaAs-based InGaAlAsP-based material may be used. In addition, although Zn is used as a dopant,
e, Mg, Cd, Se, S, Te, C may be used. Although the laser structure is a DH laser, it can be applied to a high value-added laser such as a DFB laser and a DBR laser. Further, the structure of the active layer is a PBH type, but other structures may be used. Further, in this embodiment, the modulation doping structure is applied to the laser, but it can be applied to a waveguide, a light receiving element and the like. Also, p-InGaAsP is used as a Zn stop layer.
Undoped-InP, undoped-InGa
AsP and even undoped InGa
It may be AsP.

Although the device is a laser in this embodiment, an electronic device (eg, HEMT, HFET, HBT, etc.) may be used as long as the device uses doping.

Although the MOVPE method was used as the crystal growth method, other growth methods such as a hydride VPE method may be used in addition to the gas source MBE and MOMBE methods. Further, although the method of manufacturing a semiconductor laser has been described in the embodiment, an optical waveguide can be manufactured by a similar method.

Further, although an n-type substrate is used as the conductivity of the crystal substrate, a p-type substrate is used to reduce the contact resistance between the metal of the p-side electrode and the semiconductor in the case of a high light output laser device. In this case, the additive element may be p-type.

Although a p-type dopant has been described as a dopant added to realize a modulation doping structure, an n-type dopant may be used.

[0056]

As described above, according to the present invention, there is provided a dopant diffusion stop layer comprising a crystal having a larger energy gap than the well layer and a larger solid solubility limit of the dopant than the cladding layer, and a modulation doping layer in which the diffusion of the dopant is suppressed. By adopting the structure, the differential gain can be increased, and a semiconductor laser having a low threshold value, a high slope efficiency, a high operation speed, and a low distortion can be realized.

Further, since the waveguide layers are present on both sides of the quantum well layer, the portion having the maximum optical output is located at the center of the quantum well layer, the light confinement coefficient 向上 is improved, and the optical output is increased.

[Brief description of the drawings]

FIG. 1 shows a modulation-doped MQ according to a first embodiment of the present invention.
Cross section of W laser structure

FIG. 2 is a diagram showing a structure of a modulation-doped quantum well layer and an energy state.

FIG. 3 is a diagram showing the behavior of Zn in a cladding layer and a Zn stop layer.

4A is a diagram showing the behavior of Zn in the modulation doping layer. FIG. 4B is an energy state diagram of the modulation doping layer. FIG. 4C is a diagram showing the relationship between the energy gap and the Zn saturation concentration.

FIG. 5 shows a modulation-doped MQ according to a second embodiment of the present invention.
Cross section of W laser structure

FIG. 6 shows a modulation-doped MQ according to a third embodiment of the present invention.
Cross section of W laser structure

FIG. 7 shows a modulation-doped MQ according to a fourth embodiment of the present invention.
The figure which shows the manufacturing process cross section of W laser.

FIG. 8 is a schematic diagram of a conventional modulation-doped MQW laser.

9A is a diagram showing a Be concentration distribution of a conventional modulation-doped quantum well, FIG. 9B is a diagram of a conventional modulation-doped quantum well structure, FIG. 9C is a diagram of a conventional modulation-doped quantum well structure, and FIG. Diagram of modulation-doped quantum well in the case of manufacturing a laser using modulation-doped quantum wells

FIG. 10 is a diagram showing a state of preservation of a modulation dope structure during growth of a p-InP crystal.

FIG. 11 is a diagram showing a modulation doping concentration and a storage state of a modulation doping structure.

FIG. 12 is a diagram showing the relationship between the flow rate of DMZn and the hole concentration for InP and InGaAsP.

FIG. 13 is a diagram showing a modulation doping concentration and a storage state of a modulation doping structure.

FIG. 14 is a diagram showing a cross-sectional structure and an energy level of a conventional modulation-doped quantum well.

[Explanation of symbols]

 Reference Signs List 1 Sn-doped InP substrate 2 n-InGaAsP waveguide layer 3 InGaAs well layer 4 non-doped-InGaAsP barrier layer 5 p-InGaAsP modulation-doped layer 6 non-doped-InGaAsP barrier layer 7 modulation-doped quantum well 8 p-InGaAsPZn stop layer 9 p-InP Cladding layer 10 pnp current blocking layer 11 Mesa-shaped region 12 n-side electrode made of Au / Sn 13 p-side electrode made of Au / Zn 14 p-InGaAsP strain modulation doping layer 15 non-doped-InGaAsP step-type barrier layer 16 Non-doped InGaAsP step-type barrier layer

Continuation of front page (72) Inventor Yasushi Matsui 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-2-154472 (JP, A) JP-A-2-33990 (JP) JP-A-3-77391 (JP, A) JP-A-1-181589 (JP, A) JP-A-4-162483 (JP, A) IEEE PHOTON. TECH. LETT. 2-4! (1990) P.A. 231-233

Claims (7)

(57) [Claims] And 1. A board, a first conductivity type waveguide layer on the substrate, the well layers and barrier layers are alternately laminated, and modulation doping quantum well layer modulation-doped in the barrier layer, and a stop layer for stopping the diffusion of the dopant, and the cladding layer of the second conductivity type is a structure sequentially stacked, the energy gap of the front Kishirube waveguide layer, energy of the substrate
And the Energy gap less, the well layer is, before smaller energy gap than Kishirube Namijiso, the barrier layer is in the middle of the energy gap of the prior Kishirube waveguide layer and the well layer, the conductive heat transfer to a portion A modulation doped layer having an energy gap of the stop layer , the barrier layer
Characterized in that the semiconductor laser is a crystal having an energy gap equal to or more than the above and a dopant added below the solid solubility limit. 2. The semiconductor laser according to claim 1, wherein the addition amount of the dopant in the cladding layer is equal to or less than the solid solubility limit. 3. The semiconductor laser according to claim 1, wherein the amount of the dopant added to the barrier layer is equal to or less than the solid solubility limit. 4. The distortion of the modulation doping layer is low due to doping.
4. The semiconductor laser according to claim 1 , wherein the semiconductor laser has a lattice mismatch that decreases . 5. The semiconductor laser according to claim 1 , wherein the modulation doping layer has an energy gap different from that of the barrier layer. 6. A board guide Den-type, the semiconductor laser of any one of claims 1 to 5, conductive heat transfer-type modulation doped layer is characterized in that it is a p-type both the barrier layer has. 7. A board on the steps of growing a waveguide layer that having a first conductive heat transfer-type is the energy gap of the substrate below a front Kishirube Namijiso than the energy gap is small well layer a first barrier layer of undoped intermediate energy gap between the waveguide layer and the well layer, and modulation doping layer,
Growing a modulation-doped quantum well layer in which undoped second barrier layers are alternately stacked; growing a stop layer having an energy gap equal to or larger than the barrier layer and stopping diffusion of the dopant; Is not less than the stop layer, and the second
A step of growing a cladding layer having a conduction type of: a step of etching the substrate up to the substrate in a stripe shape; and a step of forming a side surface of the stripe by a second conduction type crystal, a first conduction type crystal, and a second side surface. Growing a conductive type crystal and embedding the stripes.