JP2001257430A - Manufacturing method for semiconductor element, semiconductor manufactured thereby, and optical system using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method by which the crystallinity improvement effect of a semiconductor element including a group-III-V mixed crystal semiconductor layer containing nitrogen can easily be obtained, a crystalline semiconductor of high quality which uses the manufacturing method, and an optical system which uses the semiconductor element. SOLUTION: The semiconductor element has the group-III-V mixed crystal semiconductor layer (GaInNAs) 105 composed of a group-III element, N, and other >=1 kind of group-V element, and an upper semiconductor layer (clad layer 107) composed of one or more layers grown thereupon. The manufacturers method thereof is provided with a stage for raising the temperature to a temperature (e.g. 700 deg.C) higher than the growth temperature (e.g. 550 deg.C) of the group- III-V mixed crystal semiconductor layer between the point of time when the growth of the group-III-V mixed crystal semiconductor layer 105 ends and the point of time when the growth of the upper semiconductor layer 107 ends. This period includes the period before the upper semiconductor layer 107 formed by being doped with at least impurities begins to be grown.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a group III-V mixed crystal semiconductor device containing nitrogen (N) and another group V element having good crystallinity, and an optical communication device manufactured by the method. The present invention relates to a semiconductor device such as a semiconductor laser, a light emitting diode, a photodiode for infrared light, and an optical system using the semiconductor device, such as an optical module, an optical interconnection, or an optical communication system.

[0002]

2. Description of the Related Art Conventionally, an optical communication system using an optical fiber is mainly used in a trunk system. In the future, it is expected to be used by subscribers including households. To achieve this, it is necessary to reduce the size and cost of the system. However, in order to prevent deterioration of the high-temperature operation characteristics of the semiconductor laser for optical communication, if the device is used while being cooled by a Peltier device, the size of the system will be reduced. It is difficult to reduce the cost and price. Therefore, there is a demand for realizing a system that does not require a Peltier device for temperature control as described above, and for a semiconductor laser, a device having a high threshold temperature and a characteristic having a small characteristic change due to a temperature change is desired. However, the conventional G
It is difficult to realize a high characteristic temperature mainly due to the fact that the band discontinuity of the conduction band cannot be increased in the aInPAs / InP-based material.

As a material that can solve this problem, Japanese Patent Laid-Open No.
No. 37355 discloses that a GaInNA is formed on a GaAs substrate.
A configuration provided with an s-based material is mentioned. GaInNA
s is a group III-V mixed crystal semiconductor containing nitrogen (N) and another group V element. GaI having a larger lattice constant than GaAs
By adding nitrogen (N) to nAs, the lattice constant becomes GaAs.
s, and the band gap energy can be reduced to 1.3 μm, 1.5 μm.
A material capable of emitting light in the m band is obtained.

Also, Jpn.J.Appl.Phys.Vol.35 (199)
6) In pp. 1273-1275, Kondo et al. Calculated the band lineup. Since a GaAs lattice matching system is used, the band discontinuity of the conduction band is increased by using AlGaAs or the like for the cladding layer. For this reason, it is expected that a high characteristic temperature semiconductor laser can be realized.

However, a group III-V mixed crystal semiconductor containing nitrogen (N) and another group V element has a mixed crystal composition due to the atomic radius of nitrogen (N) being smaller than that of other elements. Most are in the immiscible region in a state of thermal equilibrium, and crystal growth is very difficult. MOCVD method (Metal
Crystals with a slight nitrogen (N) composition can be grown by Organic Chemical Vapor Deposition or MBE (Molecular Beam Epitaxy). Regarding the growth of a group III-V mixed crystal semiconductor containing nitrogen (N) and another group V element, JP-A-6-37355 discloses that a nitrogen gas or a nitrogen compound gas activated by high-frequency plasma is used as a nitrogen source. About the MOCVD method,
Japanese Patent No. 283857 discloses a MOCVD method using DMHy (dimethylhydrazine) as a nitrogen source.
JP-A-6-334168 and JP-A-11-87
No. 848 discloses an MBE method using activated nitrogen.

Further, it contains nitrogen (N) and other group V elements.
GaInNAs and GaNA which are III-V mixed crystal semiconductors
The crystallinity improvement by heat treatment after the crystal growth of s is disclosed in JP-A-11-274083 and 39th Electronic
Materials Conference, Session T, p3, Fort Collin
s, Colorado June 25-27, 1997, Appl. Phys.
Lett., Vol. 72 (1998) pp. 11409-141
1, Appl. Phys. Lett., Vol. 72 (1998) pp18
57-1859, or Jpn.J.Appl.Phys.Vol.38 (1
999) pp. L298-L300. In most cases, the heat treatment is RTA, which allows rapid heating.
(Rapid thermal annealing) device is used. Japanese Patent Application Laid-Open No. H11-274083 also describes that heat treatment is performed using a growth apparatus after the layer structure is grown.

However, these results are not an effect on the structure as a semiconductor device but PL (Photoluminescen).
ce) Results of the structure for measurement, in which an effect is obtained by performing a heat treatment after the growth of the layer structure. An example of a semiconductor device is a semiconductor laser. J. Cryst. Growth.
Vol.192 (1998) pp. In 381-385,
During the growth of the laser structure, the growth temperature of the upper cladding layer is set to GaIn which is a group III-V mixed crystal semiconductor layer containing nitrogen.
Laser oscillation in the 1.3 μm band is achieved at a temperature higher than the growth temperature of the NAs active layer. The nitrogen composition of GaInNAs is as large as 3% and lattice-matched to the GaAs substrate.

[0008]

However, with respect to the structure of a semiconductor device, a method according to the prior art, for example, as disclosed in
In the case where the heat treatment is performed after the growth of the semiconductor element structure as in Japanese Patent No. 274083, problems such as deterioration of semiconductor element characteristics due to diffusion of impurities occur. RT that can be rapidly heated
When an A (Rapid Thermal Annealing) apparatus is used, the apparatus is taken out of the growth apparatus and heat-treated by another apparatus, so that the number of manufacturing steps is increased, the number of manufacturing apparatuses is required, and the cost is increased.

Accordingly, the present invention is directed to overcoming these problems. Specifically, the method of manufacturing a semiconductor device according to the present invention is a manufacturing method capable of easily obtaining an effect of improving the crystallinity of a semiconductor device including a group III-V mixed crystal semiconductor layer containing nitrogen. It is an object of the present invention to provide a high-quality crystalline semiconductor device using the manufacturing method (claim 13) and an optical system using the semiconductor device (claims 14 and 15).

[0010]

In order to achieve the above object, a method of manufacturing a semiconductor device according to claim 1 of the present invention comprises:
A group III-V mixed crystal semiconductor layer composed of a group III element and N (nitrogen) and at least one other group V element;
In a method for manufacturing a semiconductor device having an upper semiconductor layer composed of one or more layers grown on a group-III mixed crystal semiconductor layer, the method comprises the steps of: A step of raising the temperature higher than the growth temperature of the group III-V mixed crystal semiconductor layer is provided therebetween, and the period of the step includes at least before the start of the growth of the upper semiconductor layer formed by doping impurities. It is characterized by:

After the growth of the nitrogen-containing III-V mixed crystal semiconductor layer, the crystallinity is improved by performing a heat treatment.
The effect of improving the crystallinity can also be obtained by including a step of raising the temperature higher than the growth temperature of the III-V mixed crystal semiconductor layer between the end of the growth of the III-V mixed crystal semiconductor layer and the end of the growth of the upper semiconductor layer. In this case, the heat treatment step can be performed by the same apparatus during the semiconductor element growth step without using another apparatus.
In addition, since this heat treatment step includes at least before the start of the growth of the upper semiconductor layer formed by doping the impurity, diffusion of the impurity is suppressed, and deterioration of the characteristics of the semiconductor element can be suppressed.

According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor device.
2. The method of manufacturing a semiconductor device according to claim 1, wherein
The step of raising the temperature higher than the growth temperature of the group IV-V mixed crystal semiconductor layer must be after covering the group III-V mixed-crystal semiconductor layer containing nitrogen with another upper semiconductor layer composed of at least one atomic layer. Features.

If the heat treatment is carried out with the surface of the group III-V mixed crystal semiconductor layer containing nitrogen exposed, the crystallinity near the surface is deteriorated due to desorption of group V atoms and migration of surface atoms. Although the characteristics of the element are deteriorated, heat treatment after covering with another upper semiconductor layer composed of at least one atomic layer can prevent this.

According to a third aspect of the present invention, there is provided a method of manufacturing a semiconductor device.
3. The method of manufacturing a semiconductor device according to claim 1, wherein the semiconductor device is a semiconductor laser,
The group V mixed crystal semiconductor layer is an active layer for generating light, and the semiconductor laser has at least the active layer and a lower and upper clad layer (upper semiconductor layer) for confining light.
The period of the step in which the temperature is higher than the growth temperature of the group V mixed crystal semiconductor layer (active layer) is included at least before the start of the growth of the upper clad layer formed by doping impurities. .

According to a fourth aspect of the present invention, there is provided a method of manufacturing a semiconductor device.
An upper clad layer formed by doping impurities is provided below the upper clad layer (substrate side), and a clad layer not doped with impurities is provided. Claims 5 and 6 specify an effective material and composition therefor. In claim 5, the claim 5
III-V group mixed crystal semiconductor layer having an In composition (1-x) of 25%
Ga _x In _1-x N _y As _1-y (0 ≦ x ≦ 0.7
(5, 0 <y <1), and claim 6 is that the upper semiconductor layer further includes Zn-doped GaInP.

In the case of a semiconductor laser, III-
Although the crystallinity is improved by performing a heat treatment after the growth of the group V mixed crystal semiconductor layer, the heat treatment is performed not after the growth of the semiconductor laser structure but from the end of the growth of the group III-V mixed crystal semiconductor layer containing nitrogen. III-V during the end of structure growth
The effect of improving the crystallinity can also be obtained by including a step in which the temperature is higher than the growth temperature of the group mixed crystal semiconductor layer. In this case, the heat treatment step can be performed by the same apparatus during the semiconductor laser structure growth step without using another apparatus. In addition, by including at least the time before the start of the growth of the upper cladding layer formed by doping impurities during the heat treatment step, diffusion of impurities is suppressed, and deterioration of semiconductor laser characteristics such as an increase in threshold current is suppressed. Can be suppressed.

When an upper clad layer doped with impurities is grown at a high temperature, the impurities are diffused into the active layer and cause a deterioration in the performance of the semiconductor device. Therefore, a non-doped clad layer is provided under the impurity-doped upper clad layer (substrate side), and a heat treatment is performed by growing this layer at a high temperature. By growing at lower temperatures,
This makes it possible to reduce the diffusion of impurities into the active layer and suppress the deterioration of device characteristics.

According to a seventh aspect of the present invention, there is provided a method of manufacturing a semiconductor device.
The method for manufacturing a semiconductor device according to claim 1 or 2 is applied to a surface-emitting type semiconductor laser, and the III-V mixed crystal semiconductor layer containing nitrogen is used as an active layer for generating light.
The semiconductor laser has at least lower and upper multilayer mirrors for confining light with the active layer. During the step of raising the temperature higher than the growth temperature of the group III-V mixed crystal semiconductor layer (active layer), at least the impurity is removed. And before the start of the growth of the upper semiconductor layer formed by doping. Claims 7 to 9 are effective materials for that purpose.
Claim 8 specifies the composition, wherein the III-V mixed crystal semiconductor layer has an In composition (1-x) of 25% or more.
a _x In _1-x N _y As _1-y (0 ≦ x ≦ 0.75, 0 <y <
According to the first aspect, in the ninth aspect, the upper semiconductor layer includes Zn-doped AlAs. In the tenth aspect, at least one of the lower multilayer reflector and the upper multilayer reflector is used as a high refractive index layer. Al _N Ga _1-N As (0 ≦ N <
1) As a low refractive index layer, Al _M Ga _1-M As (0 ≦ N <M
.Ltoreq.1).

In the case of a surface-emitting type semiconductor laser, the crystallinity is improved by performing a heat treatment after growing a nitrogen-containing group III-V mixed crystal semiconductor layer. The temperature is higher than the growth temperature of the nitrogen-containing III-V mixed crystal semiconductor layer between the end of the growth of the III-V mixed crystal semiconductor layer containing nitrogen and the end of the growth of the surface emitting semiconductor laser structure. The effect of improving the crystallinity can also be obtained by including the step. In this case, the heat treatment step can be performed by the same apparatus during the surface-emitting type semiconductor laser structure growth step without using another apparatus. Also, since this heat treatment step includes at least before the start of the growth of the upper semiconductor layer formed by doping with impurities, diffusion of impurities is suppressed, and the surface-emitting type semiconductor laser characteristics such as an increase in threshold current are deteriorated. Can be suppressed.

GaInNAs can be an active layer material for 1.3 μm and 1.55 μm band lasers that can be grown on a GaAs substrate, but the band gap wavelength of GaAs is 0.9 μm.
It is necessary to increase the wavelength by adding nitrogen and In, which have the effect of increasing the band gap wavelength. G
When the In composition (1-x) of aInNAs is 25% or more, the amount of added nitrogen can be reduced.

According to a eleventh aspect of the present invention, in the method of manufacturing a semiconductor device, the Ga _x In _1-x N _y As _1-y (0 ≦ x ≦ 0.75,
0 <y <1) The temperature in the step that is higher than the growth temperature of the layer is set to 780 ° C. or less.

The In composition (1-x) of GaInNAs is 2
In the case of 5% or more, that is, when the GaAs substrate has a large strain, if the heat treatment is performed at an excessively high temperature, the crystallinity may be deteriorated due to relaxation of the strain or the like, and the heat treatment may be performed at an appropriate temperature of 780 ° C. or less. is necessary.

According to a twelfth aspect of the present invention, in the method for manufacturing a semiconductor device described above,
As an example of a method for forming a group V mixed crystal semiconductor layer, MOCV
Method D (Metal Organic Chemical Vapor Deposition) or MBE (Molecular Be
am Epitaxy (molecular beam epitaxial growth method).

A semiconductor device according to a thirteenth aspect is a semiconductor device manufactured by using the above-described method for manufacturing each semiconductor device, and an optical system according to a fourteenth aspect includes an optical system including such a semiconductor device. And claim 15
Is an optical system embodied in an optical module, an optical interconnection, or an optical fiber communication system.

According to a thirteenth aspect of the present invention, there is provided the semiconductor device according to the first aspect.
After the growth of a nitrogen-containing group III-V mixed crystal semiconductor layer using the manufacturing method 2 above, the crystallinity is easily improved by performing a heat treatment in a simple process to obtain a semiconductor element having high quality and excellent reliability. Obtainable. Further, since the optical system according to the fourteenth and fifteenth aspects uses a semiconductor element having high quality and excellent reliability, a high-performance and high-reliability system can be realized.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <Experiment for Explaining the Principle of the Present Invention> In this experiment, GaInNAs was used as a group III-V mixed crystal semiconductor layer containing nitrogen.
GaAs or GaInP cladding layer is formed of GaInNAs
A heat treatment experiment is performed assuming that the growth will be at a higher temperature. A GaAs layer (0.2 μm), a GaInNAs well layer (7 nm) and a G
An aAs layer (50 nm) was grown sequentially. The growth temperature in this case was 600 ° C. In each sample, the composition ratio of In was the same (30%), and the composition ratio of nitrogen was changed. Thereafter, AsH ₃ atmosphere using a MOCVD growth system, 6
Heat treatment was performed at 80 ° C., 700 ° C., and 780 ° C. for 20 minutes.

FIG. 1 is a diagram showing PL (Photoluminescence) characteristics of each sample obtained as a result of the above experiment. In the figure, a) when the heat treatment temperature is 780 ° C. and the composition ratio of nitrogen (N) is 0.2%, b) when the heat treatment temperature is 700 ° C. and the composition ratio of nitrogen (N) is 0.2% , C) is the PL when the heat treatment temperature is 680 ° C. and the composition ratio of nitrogen (N) is 0.5%, and d) is the PL when the heat treatment temperature is 680 ° C. and the composition ratio of nitrogen (N) is 0.8%. The dotted line shows the spectrum before the heat treatment, and the solid line shows the spectrum after the heat treatment.

FIG. 1 shows that the peak wavelength shifts to the shorter wavelength side due to the heat treatment, and that the shift amount increases as the heat treatment temperature increases. At the same temperature, the amount of shift is the same between samples having different amounts of nitrogen (see c and d in the figure), and it is considered that the cause of this shift is diffusion of In.

Further, it can be seen that the emission intensity decreases at 780 ° C. (see a in the figure) and increases at other temperatures below 780 ° C. (see b, c, d in the figure). The cause of the increase is considered to be a decrease in defects in the active layer due to the heat treatment.
The cause of the decrease is considered to be crystallinity deterioration. Thus G
It has been found that when the aInNAs active layer is grown and then heat-treated at a temperature lower than 780 ° C., the crystallinity is improved, and when the heat treatment is performed at a high temperature of 780 ° C. or higher, problems occur.

<First Embodiment> A semiconductor laser according to a first embodiment of the present invention utilizing the above-described effects will be described in detail with reference to the drawings. FIG. 2 is a diagram illustrating a cross-sectional view of the semiconductor laser device according to the first embodiment. Description will be made by taking an example of an insulating film stripe type laser having the simplest structure. As a layer structure, SCH-DQW (Separate Confinement Heter)
ostructure Double Quantum Well).

An n-GaAs substrate 10 having a plane orientation of (100)
1, a Se-doped n-GaAs buffer layer 102, Se
Doped n-Ga _0.5 In _0.5 P lower cladding layer (1.5 μm)
m) 103, undoped GaAs lower light guide layer (10
0 nm) 104, undoped Ga _0.63 In _0.37 N _0.006
As _0.994 well layer and undoped GaAs barrier layer (14.
7 nm), an undoped GaAs upper light guide layer (100 nm) 106, Zn-doped p-G
a _0.5 In _0.5 P upper cladding layer (1.5 μm) 107,
Zn-doped p-GaAs contact layer (0.3 μm) 1
08 are sequentially grown.

In the above structure, the In composition x of the GaInNAs well layer was 37%, and the nitrogen composition was 0.6%. G
The thickness of the aInNAs well layer was 7.7 nm. The MOCVD method was adopted as the growth method. H ₂ was used as a carrier gas. The raw materials are TMG (trimethylgallium), TM
I (trimethylindium), AsH ₃ (arsine),
PH ₃ (phosphine), and DMH as the source of nitrogen
y (dimethylhydrazine) was used. Since DMHy decomposes at low temperatures, it is suitable for low-temperature growth at 600 ° C. or lower. In this embodiment, the GaInNAs well layer was grown at 550 ° C. In particular, when growing a quantum well layer having a large strain, low temperature growth of, for example, about 500 ° C. to 600 ° C. is preferable.

The GaAs light guide layers 104 and 106 are also Ga
Grown at 550 ° C., the same as the InNAs well layer,
After the growth of the s light guide layer 106, the growth was interrupted, the substrate temperature was raised to 700 ° C, and a heat treatment was performed for 3 minutes. Thereafter, the temperature was lowered to 620 ° C., and the Zn-doped upper GaInP cladding layer 1 was formed.
07 and a GaAs contact layer 108 were grown.
The p-side electrode 110 is formed via the insulating film 109 from which a portion serving as a current injection portion has been removed. The GaAs contact layer 108 had a structure in which portions other than the current injection portion were removed by etching. An n-side electrode 111 is formed on the back surface.

In this embodiment, after the growth of the upper light guide layer, the step of stopping the growth and raising the substrate temperature to 700 ° C. for 3 minutes and the step of growing the Zn-doped upper cladding layer 107 and the GaAs contact layer 108 at 620 ° C. This corresponds to a heat treatment step.

Although it is effective to simply grow the upper cladding layer 107 and the GaAs contact layer 108 at a temperature higher than the growth temperature of the GaInNAs well layer, the heat treatment temperature is higher than the growth temperature of the GaInNAs well layer, for example, 650 ° C. to 780 ° C. Higher temperatures are preferred.

When the Zn-doped upper cladding layer 107 is grown at such a high temperature, the doped impurity (Zn in this embodiment) becomes active region (GaInNAs active layer (well layer) and GaAs light guide layers 104 and 106). ) To increase the internal loss, thereby deteriorating the characteristics of the semiconductor laser. Therefore, the impurities (Z
The growth temperature of the cladding layer doped with n) is preferably as low as possible in order to reduce diffusion.
Therefore, it is preferable to provide a heat treatment step at a high temperature before growing the clad layer doped with the impurity.

In this embodiment, after the growth of the upper light guide layer, the substrate temperature was raised to 700 ° C. and heat treatment was performed for 3 minutes. In the heat treatment step, the heat treatment is performed after the surface of the GaInNAs well layer is not exposed but covered with another upper semiconductor layer composed of at least one atomic layer, so that the removal of group V atoms and the movement of surface atoms are performed. Therefore, the deterioration of crystallinity near the surface could be suppressed. That is, the effect can be obtained even if the heat treatment is performed while increasing the temperature during the growth of the upper light guide layer 106.

The threshold current density of the semiconductor laser thus manufactured was 1 kA / cm ² or less. The oscillation wavelength was about 1.3 μm. The characteristic temperature at 25 ° C to 80 ° C exceeded 200K and was very good. In addition, since the crystallinity was good, the life was long. The oscillation wavelength is nitrogen composition,
It could be controlled by the In composition and the thickness of the well layer.

In the above description, an example of growth by the MOCVD method has been described, but other growth methods such as the MBE method can be adopted. Although an example using DMHy as a nitrogen source has been described, activated nitrogen and other nitrogen compounds such as NH ₃ can also be used. Organic arsenic such as TBA (tertiary butyl arsine) can also be used as a raw material for arsenic (As). In the above description, a double quantum well structure (DQW) is shown as an example of a stacked structure, but a structure (SQW, MQW) using a quantum well of another number of wells may be used. The composition thickness of each layer may be set to a value other than the above as needed. For the cladding layer, AlGaAs having a wide gap can be used similarly to GaInP described above. The structure of the laser element may be other than that shown in FIG.

<Second Embodiment> A semiconductor laser according to a second embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 3 is a diagram illustrating a cross-sectional view of the semiconductor laser device according to the second embodiment. The difference from the first embodiment is that undoped GaAs
s Upper light guide layer (100 nm) 106 and Zn-doped p
-Ga _0.5 In _0.5 P upper cladding layer (1.5 μm) 10
7 undoped Ga _0.5 In _0.5 P layer (0.05 μm).
m) 112 is provided.

In this embodiment, the GaInNAs well layer is grown at 570.degree. GaAs light guide layer 10
4,106 are also grown at 570 ° C., the same as the GaInNAs well layer, and then undoped Ga _0.5 In _0.5 P layer (0.05 μm).
m) grow 112 at 720 ° C., then raise the temperature to 640 ° C.
And a Zn-doped upper GaInP cladding layer 107 and a GaAs contact layer 108 were grown.

In this embodiment, the heat treatment process is performed by growing the undoped Ga _0.5 In _0.5 P layer at 720 ° C. higher than the growth temperature of the GaInNAs layer and growing the Zn-doped upper GaInP clad layer 107 and the GaAs contact layer 108 at 640 ° C. Also serves as. At a temperature higher than the growth temperature of the GaInNAs layer, the upper cladding layer 107 and the GaAs
Although the growth of the contact layer 108 is effective,
The heat treatment temperature is preferably as high as about 700 ° C.

When the Zn-doped upper cladding layer 107 is grown at such a high temperature, the doped impurity (Zn in this embodiment) diffuses into the active region to increase the internal loss, thereby deteriorating the characteristics of the semiconductor laser. Cause it to do so. For this reason, the growth temperature of the cladding layer doped with the impurity is suitably as low as 700 ° C. or less to reduce diffusion. For this reason, it is preferable to provide a heat treatment step at a high temperature before growing the cladding layer doped with impurities.
In this embodiment, the Zn-doped upper GaInP cladding layer 1 is used.
07 is grown at a low temperature of 620 ° C. to reduce diffusion,
This is realized by providing an undoped Ga _0.5 In _0.5 P layer 112 before the doped upper GaInP cladding layer 107 and growing at a high temperature of 700 ° C. The effects such as the element characteristics were the same as those in Example 1. Since the undoped layer 112 is provided as the cladding layer, impurities hardly diffuse into the active region, so that the growth temperature of the cladding layer to be doped can be increased. The growth temperature may be the same as that of the undoped layer.
Although the undoped layer 112 is made of GaInP in this embodiment, this effect can be obtained by using a material having a larger band gap and a smaller refractive index than the optical guide layer.

<Third Embodiment> A third embodiment of the present invention will be described.
A detailed explanation of surface emitting semiconductor lasers using drawings.
I will tell. FIG. 4 shows a surface-emitting type semiconductor laser according to the third embodiment.
FIG. 3 is a diagram illustrating a structure of a user. N-G of plane orientation (100)
n-AlGaAs and n-GaAs on an aAs substrate 201
s is the thickness of 1/4 of the oscillation wavelength in each medium
N- composed of a periodic structure (35 periods) alternately stacked
Semiconductor multilayer mirror (lower multilayer mirror) 202,
Doped lower GaAs spacer layer 203, three layers of Ga_0.7
In_0.3N_0.01As _0.99As well layer and GaAs barrier layer
Quantum well (QW) active layer 204 made of
Upper GaAs spacer layer 205, Zn-doped p-Al
As layer (50 nm) 206, p-GaAs contact layer
207, undoped AlGaAs and GaAs respectively
Product with a thickness of 1/4 of the oscillation wavelength in the medium of
Semiconductor multilayer film reflection consisting of laminated periodic structure (22 periods)
Mirror 208 is grown sequentially.

Ga _0.7 In _0.3 N _0.01 As _0.99 well layer and G
Multiple quantum well (QW) active layer 2 composed of aAs barrier layer
In No. 04, the In composition x was 30% and the nitrogen composition was 1%.
The thickness of the quantum well active layer 204 was 7 nm. The MOCVD method was adopted as the growth method. The raw materials are TMG (trimethylgallium), TMI (trimethylindium),
AsH ₃ (arsine), PH ₃ (phosphine), and DMHy (dimethylhydrazine) were used as raw materials for nitrogen. Since DMHy decomposes at low temperatures, it is suitable for low-temperature growth at 600 ° C. or lower.

In this embodiment, the GaInNAs layer is 540
Grown at ℃. DMHy decomposes at low temperature, so 600
This method is suitable for low-temperature growth at a low temperature or less, and is particularly advantageous when growing a quantum well layer having a large strain that requires low-temperature growth. H ₂ was used as a carrier gas. In this embodiment, the substrate temperature was increased from 540 ° C. to 700 ° C. from the latter half of the growth of the undoped upper GaAs spacer layer 205 to before the growth of the Zn-doped p-AlAs layer 206 doped with impurities. Zn-doped p-AlA for doping impurities
The layer above the s layer 206 was grown at 650 ° C.

Next, by photolithography and an etching step, a diameter of 30 μm is
Mesa etching into a circular shape, and then the upper multilayer reflector 2
08 was mesa-etched into a circle having a diameter of 10 μm.
The AlxOy current confinement layer 2061 is made of AlA
The s layer 206 was formed by oxidizing with water vapor from the side.

Next, the etched portion is buried and flattened with polyimide, and the polyimide on the p-contact portion 209 and the upper multilayer mirror 208 serving as a light extraction port is removed.
A p-side electrode 210 was formed on the p-contact portion, and an n-side electrode 211 was formed on the back surface of the substrate.

In this embodiment, the undoped upper GaAs at 700 ° C. higher than the growth temperature of the GaInNAs layer 204 is used.
Z for doping impurities from the latter half of the growth of the spacer layer 205
The growth process before the growth of the n-doped p-AlAs layer 206 corresponds to a heat treatment process. The growth temperature of the layer to be doped with impurities is preferably as low as 700 ° C. or less in order to reduce diffusion. In the present embodiment, a heat treatment process at a high temperature is provided before the growth of the layer 206 to be doped with impurities.
The crystallinity of the InNAs well active layer 204 is improved.

The oscillation wavelength of the surface emitting laser manufactured by the above manufacturing method was about 1.3 μm. Threshold current density is 1k
A / cm ² or less. The characteristics at high temperatures were also good. Furthermore, since the crystallinity was good, the life was long.

In the above description, an example of the growth by the MOCVD method has been described, but other growth methods such as the MBE method can be used. In addition, although an example in which DMHy is used as the nitrogen source has been described, activated nitrogen and other nitrogen compounds such as NH ₃ may be used. Further, an example of a triple quantum well structure (TQW) has been described as a laminated structure, but a structure (SQW, MQW) using a quantum well of another number of wells or the like can also be used.
The composition thickness and the like of each layer can be set to values other than the above as needed. The structure of the laser may be other than the above. In this embodiment, the p-contact layer 207 is provided below the upper multilayer reflector 208, but a structure in which the contact portion 207 is provided above the upper multilayer reflector 208 may be adopted. Although the multilayer film reflecting mirror is made of a combination of AlGaAs and GaAs, any structure may be used as long as a high refractive index and a low refractive index are alternately laminated. In the case of an AlGaAs-based material, Al _N Ga _{1 -N is used} as a high refractive index layer. As (0 ≦ N <1), and the low refractive index layer can be composed of Al _M Ga _1-M As (0 ≦ N <M ≦ 1). Also, GaInP / GaAs, etc.
Other material systems can be used. Further, although an example has been shown in which the upper multilayer film reflecting mirror 208 and the lower multilayer film reflecting mirror 202 are formed of a semiconductor material, one or both of these mirrors may be formed of a dielectric material.

In the present invention, Ga _x In _{1 -x} N _y As _{1 -y} (0 ≦ x ≦
The present invention can be applied to various semiconductor elements using a group III-V mixed crystal semiconductor containing nitrogen (N) such as 1,0 <y <1) and another group V element.

According to the present invention, since the temperature characteristics of the semiconductor laser are very excellent, it can be used for an optical communication system which does not require a cooling element. Not only can it be used for long-distance communication using optical fibers, but also between devices such as computers, between boards, between LSIs in boards,
It can be used for short-distance communication as optical interconnection, such as between elements within I.

In particular, the surface emitting laser can reduce the power consumption by orders of magnitude as compared with the edge emitting laser, and can be easily formed into a two-dimensional array. As the wavelength, the 1.3 μm band and the 1.55 μm band where the transmission loss of the optical fiber is small are preferable, but a surface emitting laser having an oscillation wavelength of 1.3 μm and 1.55 μm with satisfactory performance has not been realized. . According to the present invention, since a semiconductor element containing GaInNAs having good crystallinity can be manufactured, an optical system such as a high-performance optical transceiver module, optical interconnection, or optical fiber communication system can be realized.

[0055]

According to the present invention, the following effects can be obtained. (Effect of Claim 1) The crystallinity is improved by performing a heat treatment after the growth of a nitrogen-containing group III-V mixed crystal semiconductor layer. The effect of improving the crystallinity can also be obtained by including a step of raising the temperature above the growth temperature of the III-V mixed crystal semiconductor layer between the end of the growth of the group V mixed crystal semiconductor layer and the end of the growth of the upper semiconductor layer. In this case, the heat treatment step can be performed by the same apparatus during the semiconductor element growth step without using another apparatus. Further, since this heat treatment step includes at least before the start of the growth of the upper semiconductor layer formed by doping the impurities, diffusion of the impurities can be suppressed, and deterioration of the characteristics of the semiconductor element can be suppressed. Is obtained.

(Effect of Claim 2) If the heat treatment is performed while the surface of the nitrogen-containing group III-V mixed crystal semiconductor layer is exposed, the crystallinity near the surface due to desorption of group V atoms and movement of surface atoms. Is deteriorated, and as a result, the characteristics of the semiconductor element are deteriorated. However, if the heat treatment is performed after the semiconductor element is covered with another upper semiconductor layer composed of at least one atomic layer, this can be prevented, and the semiconductor element having good crystallinity can be prevented. Can be obtained.

(Effects of Claims 3 to 6) In the case of a semiconductor laser, the crystallinity is improved by performing a heat treatment after growing a group III-V mixed crystal semiconductor layer containing nitrogen, but after growing the semiconductor laser structure. Without heat treatment, containing nitrogen III-
The effect of improving the crystallinity can also be obtained by including a step of raising the temperature above the growth temperature of the III-V mixed crystal semiconductor layer between the end of the growth of the group V mixed crystal semiconductor layer and the end of the growth of the semiconductor laser structure. In this case, the heat treatment step can be performed by the same apparatus during the semiconductor laser structure growth step without using another apparatus. In addition, by including at least the time before the start of the growth of the upper cladding layer formed by doping impurities during the heat treatment step, diffusion of impurities is suppressed, and deterioration of semiconductor laser characteristics such as an increase in threshold current is suppressed. And a high-quality semiconductor element can be obtained. When the upper clad layer doped with impurities is grown at a high temperature, the impurities diffuse into the active layer and deteriorate the performance of the semiconductor device. By providing a clad layer not doped with an impurity and performing a heat treatment by growing this layer at a high temperature, the upper clad layer doped with the impurity can be grown at a lower temperature. As a result, diffusion of impurities into the active layer can be reduced, and a high-quality semiconductor element can be obtained.

Claims 5 and 6 specify the composition. GaInNAs can be used as an active layer material for 1.3 μm and 1.55 μm band lasers that can be grown on a GaAs substrate. However, GaAs has a band gap wavelength of about 0.9 μm, and nitrogen and In have an effect of increasing the band gap wavelength. , It is necessary to increase the wavelength. As described in claim 4, the In composition (1-x) of GaInNAs is 2
When the content is 5% or more, the amount of added nitrogen can be reduced, and a high-quality semiconductor device (surface-emitting type semiconductor laser) can be obtained.

(Effects of Claims 7 to 10) In the case of a surface-emitting type semiconductor laser, the crystallinity is improved by performing a heat treatment after growing a group III-V mixed crystal semiconductor layer containing nitrogen.
The heat treatment is performed not after the growth of the surface-emitting type semiconductor laser structure but between the time when the growth of the group III-V mixed crystal semiconductor layer containing nitrogen and the time when the growth of the surface-emitting semiconductor laser structure is completed.
The effect of improving the crystallinity can also be obtained by including a step in which the temperature is higher than the growth temperature of the group V mixed crystal semiconductor layer. In this case, the heat treatment step can be performed by the same apparatus during the surface-emitting type semiconductor laser structure growth step without using another apparatus. Also, since this heat treatment step includes at least before the start of the growth of the upper semiconductor layer formed by doping with impurities, diffusion of impurities is suppressed, and the surface-emitting type semiconductor laser characteristics such as an increase in threshold current are deteriorated. And a high-quality semiconductor device (surface emitting semiconductor laser) can be obtained.

Claims 8 to 10 specify the composition and structure. GaInNAs can be an active layer material for 1.3 μm and 1.55 μm band lasers that can be grown on a GaAs substrate, but the band gap wavelength of GaAs is 0.9 μm.
It is necessary to increase the wavelength by adding nitrogen and In, which have an effect of increasing the band gap wavelength, which is about m.
As described in claim 7, the In composition of GaInNAs (1-
When x) is 25% or more, the amount of added nitrogen can be reduced, and a high-quality semiconductor device (surface emitting semiconductor laser) can be obtained.

(Effect of Claim 11) GaInNA
When the In composition (1-x) of s is 25% or more, that is, G
If the aAs substrate has a large strain, if heat treatment is performed at an excessively high temperature, the crystallinity may be deteriorated due to relaxation of the strain or the like. By performing the heat treatment at an appropriate temperature of 780 ° C. or lower, the crystallinity may be reduced. An improved and high-quality semiconductor device can be obtained.

(Effect of Claim 12) Nitrogen-containing
The group III-V mixed crystal semiconductor layer can be realized by a conventionally known film forming method.

(Effects of Claims 13 to 15) Using the above-described production method of claims 1 to 12, a nitrogen-containing III
After the growth of the group-V mixed crystal semiconductor layer, the crystallinity is easily improved by performing a heat treatment in a simple step, and a high quality and highly reliable semiconductor element can be obtained without increasing the cost. Item 13). Further, a high-performance and highly-reliable optical system can be realized by using the high-quality and highly reliable semiconductor element.
5).

[Brief description of the drawings]

FIG. 1 shows the PL (Photoholumi) of each sample obtained as a result of the experiment.
FIG.

FIG. 2 is a cross-sectional view of the semiconductor laser device according to the first embodiment.

FIG. 3 is a sectional view of a semiconductor laser device according to a second embodiment.

FIG. 4 is a diagram showing a structure of a surface emitting semiconductor laser according to a third embodiment.

[Explanation of symbols]

101: n-GaAs substrate 102: n-GaAs buffer layer _{103: n-Ga 0.5 In 0.5} P lower cladding layer 104: an undoped GaAs lower optical guide layer 105: an active layer 1051: GaInNAs well layer 1052: GaAs barrier layer 106: GaAs Upper light guide layer 107: p-GaInP upper cladding layer 108: p-GaAs contact layer 109: insulating layer (SiO ₂ ) 110: p-side electrode 110 111: n-side electrode 112: GaInP layer 201: n-GaAs substrate 202: n-semiconductor multilayer mirror (lower multilayer mirror) 203: lower GaAs spacer layer 204: multiple quantum well (QW) active layer composed of GaInNAs well layer and GaAs barrier layer 205: upper GaAs spacer layer 206: p-AlAs Layer 207: p-GaAs contact Layer 208: semiconductor multilayer reflection mirror 209: p contact portion 210: p-side electrode 211: n-side electrode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K030 AA11 BA38 BA55 BA56 BB12 CA04 JA06 LA14 5F041 AA40 CA04 CA05 CA34 CA35 CA36 CA40 CA65 CA66 CA73 5F045 AA04 AB09 AB10 AB17 AB18 AC01 AC07 AC08 AC19 AD09 AD10 AF04 AF13 BB12 CA53 DA EB15 HA16 5F073 AA46 AA74 AB17 BA01 CA17 CB02 DA05 EA28

Claims (15)

[Claims] 1. A group III-V mixed crystal semiconductor layer comprising a group III element, N (nitrogen) and at least one other group V element, and an upper part of the group III-V mixed crystal semiconductor layer. Grown one
A method of manufacturing a semiconductor device having an upper semiconductor layer comprising a plurality of layers or a plurality of layers, wherein the III-V mixed crystal semiconductor is formed between the time when the growth of the III-V mixed crystal semiconductor layer is completed and the time when the growth of the upper semiconductor layer is completed. Manufacturing a semiconductor element, wherein a step of raising the temperature to a temperature higher than the growth temperature of the layer is provided, and the period of the step includes at least before the start of growth of the upper semiconductor layer formed by doping impurities. Method. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the step of setting the temperature higher than the growth temperature of the group III-V mixed crystal semiconductor layer includes the step of setting the group III-V mixed crystal semiconductor layer to at least one.
A method for manufacturing a semiconductor device, which is performed after covering with another upper semiconductor layer made of an atomic layer. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the semiconductor device is a semiconductor laser, and the III-V mixed crystal semiconductor layer is an active layer that generates light. Is a period of a step of having at least a growth temperature of the III-V mixed crystal semiconductor layer (active layer), which has at least a lower cladding layer for confining light with the active layer and an upper cladding layer serving as the upper semiconductor layer. Comprises at least before the start of growth of an upper cladding layer formed by doping impurities. 4. The method of manufacturing a semiconductor device according to claim 3, further comprising a non-impurity-doped cladding layer below (on the substrate side) an upper cladding layer formed by doping with an impurity. A method for manufacturing a semiconductor device. 5. The method of manufacturing a semiconductor device according to claim 1, wherein the III-V mixed crystal semiconductor layer has an In composition (1-x) of 25% or more. _x In _1-x N _y As _1-y (0 ≦ x ≦
0.75, 0 <y <1). 6. The method according to claim 5, wherein the upper semiconductor layer contains Zn-doped GaInP. 7. The method for manufacturing a semiconductor device according to claim 1, wherein said semiconductor device is a surface emitting semiconductor laser,
The IV group mixed crystal semiconductor layer is an active layer for generating light, the surface emitting semiconductor laser has at least a lower multilayer reflector and an upper multilayer reflector for confining the active layer and light, and the III. The period of the step of raising the temperature higher than the growth temperature of the group V mixed crystal semiconductor layer (active layer) includes at least before the start of the growth of the upper semiconductor layer formed by doping impurities. Production method. 8. The method for manufacturing a semiconductor device according to claim 7, wherein the III-V mixed crystal semiconductor layer has a Ga _x In ₁ -xN _y As having an In composition (1-x) of 25% or more. _1-y (0 ≦ x ≦
0.75, 0 <y <1). 9. The method of manufacturing a semiconductor device according to claim 7, wherein the upper semiconductor layer includes Zn-doped AlAs. 10. The semiconductor manufacturing method according to any one of claims 7 to 9, wherein at least one of the lower multilayer mirror and the upper multilayer reflection mirror, Al _N Ga as a high refractive index layer _{1- N} As (0 ≦
N <1), Al _M Ga _1-M As (0 ≦ N) as the low refractive index layer
A method for manufacturing a semiconductor device, comprising a structure in which <M ≦ 1) are alternately stacked. 11. The method for manufacturing a semiconductor device according to claim 1, wherein the temperature of the step of raising the temperature higher than the growth temperature of the GaInNAs layer is 780 ° C. or less. Semiconductor device manufacturing method. 12. The method of manufacturing a semiconductor device according to claim 1, wherein the group III-V mixed crystal semiconductor layer is formed by MOCVD (Metal Oxide Method).
A method of manufacturing a semiconductor device, which is formed by rganic chemical vapor deposition (MBM) or MBE (Molecular Beam Epitaxy). 13. A semiconductor device manufactured by using the method for manufacturing a semiconductor device according to claim 1. Description: 14. An optical system comprising the semiconductor device according to claim 13. 15. The optical system according to claim 14, wherein the optical system is an optical module, an optical interconnection, or an optical fiber communication system.