JP2000188442A - Semiconductor laser element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser element assuring excellent laser characteristic and including a structure to make high the product yield, and a semiconductor laser having excellent laser characteristic and high output characteristic during the high temperature operation. SOLUTION: This element has a laminated structure consisting of n-InP substrate 21, and n-InP clad layer 22, SCH-MQW active layer 23, first p-In clad layer 24, p-AlInAs/AlGaInAs layer 25, second p-InP clad layer 26, and p-GaInAs contact layer 27 sequentially formed on the n-InP substrate 21. The p-AlInAs/p-AlGaInAs layer 25 is a multi-layer film holding the upper and lower surfaces of the p-AlInAs layer 25a with the p-AlGaInAs (λg=1.1 μm) layer. The laminated structure is formed at its upper part as the striped ridge 32 having the width of about 10 μm. The ridge side surface of the p-AlInAs/p- AlGaInAs layer 25 is formed as the Al oxide film 28 where the Al is selectively oxidized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device having a current and light confinement structure using an Al oxide layer, and more particularly, to a semiconductor laser device having good laser characteristics and a high product yield. And a semiconductor laser device exhibiting good laser characteristics and high output characteristics during high-temperature operation and high-speed operation.

[0002]

2. Description of the Related Art In a semiconductor laser device, a semiconductor layer containing Al is formed as a part of a laminated structure of a light emitting region, and Al in the semiconductor layer containing Al is selectively oxidized to form an Al oxide layer. The Al oxide layer is used as a current blocking layer, that is, a current confinement structure.

Here, a configuration of a conventional semiconductor laser device using an Al oxide layer as a current blocking layer will be described with reference to FIG. FIG. 4 is a schematic sectional view of a conventional semiconductor laser device. The conventional semiconductor laser device 15 is an edge-emitting type semiconductor laser device. As shown in FIG. 4, an n-InP substrate 1 having a thickness of about 100 μm and an n-InP
The n-InP cladding layer 2, the SCH-MQW active layer 3, the first p-InP cladding layer 4, the p-AlInAs layer 5, the second p-InP cladding layer 6, which are sequentially formed on the P substrate 1, And a p-GaInAs contact layer 7. The first p-
An upper layer portion of the InP cladding layer 4, a p-AlInAs layer 5,
Second p-InP cladding layer 6 and p-GaInAs
The contact layer 7 is formed as a stripe-shaped ridge 12 having a width of about 10 μm. Also, p-AlInAs
The side surface of the ridge of the layer 5 is made of Al selectively oxidized.
The oxide layer 8 is formed.

An SiN _x film 9 is formed as a protective film on the region other than the region above the ridge which is the window 13. The p-side electrode 10 is formed on the SiN _x film 9 including the region of the window 13 above the ridge, and the n-side electrode 11 is formed on the back surface of the n-InP substrate.

In the semiconductor laser device 15, since the Al oxide layer 8 has an electrical insulating property and the refractive index is also reduced optically, the Al oxide film 8 can confine current and light. An excellent confinement structure is formed.

Next, a method of manufacturing the conventional semiconductor laser device 15 will be described with reference to FIG. FIGS. 5A to 5C are vertical cross-sectional views each showing a cross-section of a substrate in each step when manufacturing the conventional semiconductor laser device 15. First, an n-InP cladding layer 2, an SCH-MQW active layer 3, a first p-InP cladding layer 4, and p-AlInAs are sequentially formed on an n-InP substrate 1 by MOCVD.
Layer 5, second p-InP cladding layer 6, and p-GaI
The nAs contact layer 7 is formed to form a laminated structure as shown in FIG. Next, a mask 14 made of a SiO ₂ film is formed on the contact layer 7, and then the contact layer 7, the second p-InP clad layer 6, and the p-AlInAs layer 5 are etched using the mask 14. Then, the first p-InP clad layer 4 is removed by etching halfway, thereby forming a stripe-shaped ridge having a width of 10 μm as shown in FIG. 5B. Next, the mask 14 is removed, and a heat treatment is performed at a temperature of about 500 ° C. for 150 minutes in steam to obtain p-AlI.
Al of the nAs layer 5 is selectively oxidized from the side of the ridge,
As shown in FIG. 5C, an Al oxide layer 8 is formed.

Next, a SiN _x film 9 is formed as a protective film on the region other than the region above the ridge serving as the window 13. Subsequently, the back surface of the substrate is polished so that the thickness of the n-InP substrate 1 is about 100 μm, and the p-side electrode 10 is placed on the SiN _x film 9 including the region of the window 13 above the ridge, and An n-side electrode 11 is formed on each of the back surfaces of the substrate.

[0008] The above-described method for manufacturing a semiconductor laser device is as follows.
Except for the formation of the confinement structure, it is basically the same as the method of manufacturing a normal ridge type edge emitting semiconductor laser device, but has the following advantages. That is, in the above-described manufacturing method, the confinement structure can be formed by a single crystal growth and oxidation step in which the p-AlInAs layer 5 is crystal-grown and then oxidized.
A semiconductor layer is formed, a ridge structure is embedded, and pn
As compared with a normal method of forming a confinement structure formed by junction separation, the manufacturing process is simpler, and improvement in device yield and cost reduction can be expected.

[0009]

In the edge-emitting type semiconductor laser device having the conventional structure described above, when forming the Al oxide layer, as described above, the AlInAs layer is oxidized at a high temperature of about 500 ° C. It is necessary to form an Al oxide layer by processing. However, as a result of applying such a high-temperature heat treatment to the semiconductor multilayer structure, there is a problem that cavities 16 are generated at the interface between the Al oxide layer 8 and the InP layers 4 and 6, as shown in FIG. The presence of the cavity 16 at the interface between the Al oxide layer 8 and the InP layers 4 and 6 may affect the device characteristics and reliability of the semiconductor laser device. It was difficult to improve product yield.

Accordingly, a first object of the present invention is to solve the above-mentioned problems and to provide a semiconductor laser device having good laser characteristics and a structure capable of increasing the product yield.

In the edge emitting semiconductor laser device having the above-described conventional configuration, when current is injected into the active layer, the current passes from the p-InP layer 6 to the p-AlInAs layer 5 and the p-InP layer 4, the active layer 3 is reached. Here, referring to FIG. 10, p-InP layer 6, p-AlI
The band structure of the hetero junction of the nAs layer 5 and the p-InP layer 4 will be described. FIG. 10 shows the p-InP layer 6 and p-AlIn
FIG. 4 is a schematic diagram showing a band structure of a hetero junction of an As layer 5 and a p-InP layer 4. AlInAs layer 5 and InP layer 4,
As shown in FIG. 10, since the magnitude of the bandgap energy differs from that of No. 6, a heterospike occurs near the boundary. The heterospike causes an increase in the differential resistance (= operating voltage) of the element. This increase in the differential resistance becomes remarkable especially near the rising voltage. Also,
Since the hole has a heavier mass than the electron, the effect of the heterospike on the portion where the hole feels a barrier (the region indicated by the arrow in FIG. 10) is large. This increase in differential resistance causes a decrease in laser characteristics during high current injection, high temperature operation, and high speed operation.

In order to avoid the occurrence of hetero spikes, there are two possible solutions. One is to remove the p-AlInAs layer 5 in the current injection path. However, this countermeasure may increase the number of crystal growth times of the compound semiconductor layer, increase the manufacturing cost, and may cause an unexpected problem due to a complicated laser structure.

The second countermeasure is 5 × 10 ¹⁸ cm ^−3.
By doping the p-AlInAs layer 5 so as to have the above carrier concentration, the effect of hetero spikes is reduced. By the way, p on both sides of the ridge
-The p-AlInAs layer 5 provided for selectively oxidizing Al in the AlInAs layer to form an Al oxide layer 8 to function as a current blocking layer needs to be disposed as close to the active layer as possible. However, when the carrier concentration of the p-AlInAs layer 5 is increased as in this countermeasure,
There is a concern that the laser characteristics may be degraded due to free carrier absorption of the p-AlInAs layer 5 or the laser characteristics may be degraded due to diffusion of the dopant into the active layer.

Therefore, a second object of the present invention is to provide AlIn
An object of the present invention is to provide a semiconductor laser device having a configuration that prevents an increase in operating voltage of the device due to a heterospike generated near a boundary between an As layer and an InP layer with a simple structure.

[0015]

First, in order to achieve the first object, the present inventor has made the following in order to elucidate the phenomenon that a cavity is generated between an Al oxide layer and an InP layer. Experiment was performed. First, as shown in FIG.
A three-layered film sample A in which the upper and lower surfaces of an As layer are sandwiched between InP layers;
As shown in FIG. 7B, the upper and lower surfaces of the AlInAs layer are G
a Sample B having a three-layer film sandwiched between InAs layers was prepared. Then, the samples A and B were oxidized in steam at a temperature of 500 ° C., and the cross section was observed. In the sample A, it was observed that a cavity was generated between the Al oxide layer and the InP layer. In B, the generation of voids between the Al oxide layer and the GaInAs layer could not be confirmed. The present inventor has found from the above experiments that no cavity is generated when the layer sandwiching both surfaces of the AlInAs layer is a semiconductor layer containing As. It has also been found that one surface of the AlInAs layer may be in contact with the semiconductor layer containing As.

Therefore, in order to achieve the first object, based on the above findings, a semiconductor laser device according to the present invention (hereinafter, referred to as a first invention) is formed on a semiconductor substrate. In a semiconductor laser device in which a confinement structure is formed by an Al oxide layer formed by selectively oxidizing Al in a semiconductor layer containing Al, the confinement structure includes an Al oxide layer and an Al oxide layer, as viewed in a plane parallel to the semiconductor substrate. And a semiconductor layer containing Al which is continuous with the oxide layer, wherein the semiconductor layer containing As is present on at least one surface in the stacking direction of the Al oxide layer and the semiconductor layer containing Al.

In the case where the semiconductor layer containing As is an InP substrate, an AlGaInAs layer, a GaInAsP layer, a GaI
a semiconductor layer formed of at least one of an nAs layer and an InAsP layer, for example, AlGaIn
Even as a single-layer film of an As layer, an AlGaInAs layer, a GaInA
A multilayer film of an sP layer and an InAsP layer may be used. G
When the cladding layer is a semiconductor layer containing P in the aAs substrate, the semiconductor layer containing As is a semiconductor layer formed of at least one layer of AlGaInAs and AlGaAs layers, and may be a single layer film of AlGaInAs layer. , Al
It may be a two-layer film of a GaInAs layer and an AlGaAs layer.
Since the band gap of the GaInAs layer and the InAsP layer is usually larger than that of the material of the active layer, a loss occurs when the GaInAs layer and the InAsP layer are adjacent to the active layer. Therefore, the layer thickness is preferably several nm or less.

Next, in order to achieve the second object, the present inventor has found that a heterospike has a small difference between the bandgap energy of the AlInAs layer and the bandgap energy of the InP layer. Then, it was considered that a heterospike occurred, and the problem was a heterospike on the heavier hole side, that is, on the valence band side. Therefore, the heterospike on the valence band side generated near the boundary between the AlInAs layer and the InP layer is made smooth (small).
In order to achieve the second object, the main part of the constituent elements is the same semiconductor laser element as that of the first invention, including As, lattice-matched to the InP substrate, and AlInAs.
GaInA having a band gap wavelength of 1.1 μm, for example, having a valence band side energy intermediate between the valence band side energy of the InP layer and the valence band side energy of the InP layer.
interposing an sP layer between the AlInAs layer and the InP layer;
The idea was to reduce the magnitude of the band discontinuity by changing the valence band energy stepwise.

Then, as shown in FIGS. 11A and 11B, semiconductor laser devices of samples 1 and 2 having a laminated structure including an AlInAs layer were manufactured, respectively.
The laser characteristics were evaluated. Incidentally, the semiconductor laser device of the sample 2 has the same configuration as the conventional semiconductor laser device 15 shown in FIG. FIGS. 11A and 11B are schematic diagrams showing a stacked structure including the AlInAs layers of the semiconductor laser devices of Sample 1 and Sample 2, respectively.

The semiconductor laser device of Sample 1 is shown in FIG.
As shown in FIG.
Between the InP layers 4 and 6 and the p-AlInAs layer 5, a p-Ga layer having a band gap wavelength of 1.0 μm and a film thickness of 20 nm.
This is a semiconductor laser device in which a two-layer film of an InAsP layer 35 and a p-GaInAsP layer 36 having a band gap wavelength of 1.1 μm and a thickness of 20 nm is interposed. Specifically, sample 1
11A, the p-InP layer 4 and the p-GaInAs are formed with the active layer 3 facing down, as shown in FIG.
P layer 35, p-GaInAsP layer 36, p-AlInA
s layer 5, p-GaInAsP layer 36, p-GaInAs
It has a laminated structure of a P layer 35 and a p-InP layer 6. P-InP layer 4 and p-GaIn of the semiconductor laser device of Sample 1
AsP layer 35, p-GaInAsP layer 36 and p-Al
The carrier concentration of the InAs layer 5 is 5 × 10 ¹⁷
cm ⁻³ , ridge width 4 μm, resonator length 60
0 μm.

On the other hand, the semiconductor laser device of Sample 2 is shown in FIG.
As shown in FIG. 1B, the same p-InP layer 4, p-AlInAs layer 5, and p-I
It has a stacked structure of nP layers 6 and, like the semiconductor laser device of sample 1, the carrier concentration of each layer is 5 ×
The width is about 10 ¹⁷ cm ^-3 , the ridge width is 4 μm, and the resonator length is 600 μm.

Next, injection current versus applied voltage (IV) characteristics and differential resistance (dV / dl) of the semiconductor laser devices of Sample 1 and Sample 2 were measured. The result is shown in FIG.
And (b). FIG. 12A and FIG.
(B) shows the current-voltage (IV) characteristics and the differential resistance (dV / d) of the semiconductor laser devices of Sample 1 and Sample 2, respectively.
It is a graph which shows dl).

As can be seen from FIGS. 12A and 12B, 1
The operating voltage at 00 mA was 1.44 V for the semiconductor laser device of Sample 1 and the conventional semiconductor laser device (Sample 2).
It is 1.58V. Therefore, Sample 1 in which a GaInAsP layer was inserted at the interface between the AlInAs layer and the InP layer
It can be seen that in the semiconductor laser device described above, an increase in operating voltage due to heterospikes is suppressed.

As for the differential resistance (dV / dI), the differential resistance of the semiconductor laser device of Sample 1 is significantly smaller than that of the conventional semiconductor laser device (Sample 2) in a region where the injection current is small. For example, at 20 mA, the differential resistance of the semiconductor laser of Sample 1 is about 5Ω, while the differential resistance of the semiconductor laser of Sample 2 is about 6.2Ω.

The same configuration as that of the semiconductor laser devices of Samples 1 and 2 was adopted, and the ridge width was 4 μm and the cavity length was 400 μm.
The semiconductor lasers of Samples 3 and 4, each having a high reflection film having a reflectivity of 96% on the rear end face, were prototyped, and their current-to-light output characteristics were measured. The result is as shown in FIG. As can be seen from FIG. 13, although there is no difference in the threshold current between the semiconductor laser devices of Sample 3 and Sample 4, at the time of high current injection of 100 mA or more,
A difference occurs in the luminous efficiency, so that the semiconductor laser device of Sample 3 can obtain a higher optical output than the semiconductor laser device of Sample 4 (the same configuration as the conventional semiconductor laser device). this is,
This is the effect of reducing the differential resistance by the GaInAsP layer.

Next, as the characteristic temperature (T ₀ ) indicating the temperature dependence of the threshold current of the semiconductor laser device increases, the temperature dependence of the threshold current decreases as the characteristic temperature (T ₀ ) increases. In the temperature range of 20 ° C. to 85 ° C., a characteristic temperature (T ₀₎ of the semiconductor laser element of the sample 1 is 60K, the characteristic temperature of the conventional semiconductor laser element (Sample 2) (T ₀₎ is a 53K. Therefore, the temperature dependence of the threshold current is also lower than that of GaInA.
It can be seen that the suppression is improved by inserting the sP layer.

From the above, the InP layer and AlInAs
The GaInAsP layer inserted between the AlIn
It was found that the magnitude of the band discontinuity on the valence band side generated at the interface between the As layer and the InP layer can be effectively reduced. In the above-described experiment, the semiconductor laser device of Sample 1 was composed of the p-GaInAsP layer 35 and the p-GaInAsP
The layer 36 is formed on both upper and lower sides of the p-AlInAs layer 5 by p-In.
It is interposed between the P layer 4 and the p-GaI layer.
The nAsP layer 35 and the p-GaInAsP layer 36 are p-A
It is not necessary to intervene between the p-InP layer 4 on the upper and lower surfaces of the lInAs layer 5 and at least the p-A
The p-GaInAsP layer 35 and the p-GaInAsP layer 3 between the p-InP layer 4 on the active layer side surface of the lInAs layer 5.
It has been confirmed that almost the same effect can be obtained by interposing No. 6.

In the above experiment, the semiconductor laser device of the sample 1 was composed of the p-GaInAsP layer 35 and the p-GaIn
The two-layered film of the AsP layer 36 is formed by p-AlInAs layer 5 and p-
Between the InP layer 4 and between the p-AlInAs layer 5 and p-I
Although interposed between the nP layer 6 and the nP layer 6, it is not always necessary to interpose a two-layer film.
It has been confirmed that substantially the same effect can be obtained by interposing a single layer or a multilayer of a GaInAs layer having a composition of a P layer, preferably a band gap wavelength of 0.95 μm or more and 1.15 μm or less.

Therefore, another semiconductor laser device according to the present invention (hereinafter, referred to as a second invention) is based on the above-mentioned findings, and is based on the fact that Al in a semiconductor layer containing Al formed on a semiconductor substrate is removed. In a semiconductor laser device in which a confinement structure is constituted by an Al oxide layer selectively oxidized, the confinement structure includes an Al oxide layer and a semiconductor including Al continuous with the Al oxide layer when viewed in a plane parallel to the semiconductor substrate. And at least a P-type cladding layer,
between the semiconductor layer containing Al and the cladding layer, in contact with at least the surface on the active layer side of both surfaces of the semiconductor layer containing Al,
A semiconductor layer having an energy on the valence band side intermediate between the valence band side energy of the semiconductor layer containing Al and the valence band side energy of the cladding layer is present.

By having a semiconductor layer containing As containing energy having a valence band side intermediate between the valence band side energy of the Al-containing semiconductor layer and the valence band side energy of the cladding layer, The operating voltage of the semiconductor laser device is reduced (the differential resistance is reduced) by reducing the band discontinuity on the valence band side, the light output characteristics at the time of high current injection are good, and the threshold value at the time of high temperature operation is obtained. A semiconductor laser device with low current and good characteristics can be obtained. Preferably, A
By interposing a multilayer film of a semiconductor layer containing As in which the energy on the valence band changes stepwise between the semiconductor layer containing 1 and the cladding layer, heterospikes on the valence band side can be further reduced. can do.

Specifically, the semiconductor substrate is an InP substrate, the cladding layer is an InP layer, and the semiconductor layer containing Al is an AlInAs layer, and the semiconductor layer containing As is:
The GaInAsP layer has a band gap wavelength of 0.95 μm or more and 1.15 μm or less.

[0032]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment 1 This embodiment is an example of the embodiment of the semiconductor laser device according to the first invention. FIG. 1 is a cross-sectional view showing a laminated structure of the semiconductor laser device of this embodiment, and FIG. FIG. 3 is a cross-sectional view illustrating a configuration of a current confinement layer (oxidized layer) of the semiconductor laser device according to the embodiment. The semiconductor laser device 20 according to the present embodiment includes an n-InP substrate 21 having a thickness of about 100 μm,
-N-InP cladding layer 22, SCH-MQW active layer 23, first p-I formed sequentially on InP substrate 21
nP cladding layer 24, p-AlInAs / p-AlGa
It has a laminated structure composed of an InAs layer 25, a second p-InP cladding layer 26, and a p-GaInAs contact layer 27. p-AlInAs / p-AlGa InA
As shown in FIG. 2, the s layer 25 is formed of the p-AlInAs layer 2.
The upper and lower surfaces of 5a are p-AlGa InAs (λg <1.2 μm).
m) It has a multilayer structure sandwiched between layers 25b. Here, the reason for defining p-AlGa InAs with .lambda.g <1.2 .mu.m is to reduce absorption of light in the 1.3 .mu.m band. Also, for light in the 1.5 μm band, for example, the bandgap wavelength must be smaller than λg = 1.3 μm.

In the laminated structure, the upper part of the first p-InP clad layer 24, p-AlInAs / p-AlGaI
The nAs layer 25, the second p-InP cladding layer 26, and the p-GaInAs contact layer 27 have a width of about 10 μm.
Is formed as a stripe-shaped ridge. The ridge side surface of the p-AlInAs / p-AlGaInAs layer 25 is an Al oxide layer 28 in which Al is selectively oxidized.

An SiN _x film 29 is formed as a protective film on the region other than the region above the ridge which is the window 30. Then, the p-side electrode 31 is formed on the SiN _x film 29 including the region of the window 30 above the ridge, and the n-side electrode 32 is formed of n-In.
Each is formed on the back surface of the P substrate.

Referring to FIG. 3, a method for fabricating the semiconductor laser device of this embodiment will be described. 3 (a) to 3 (c)
FIG. 3 is a cross-sectional view of a substrate showing a laminated structure in each step when manufacturing the semiconductor laser device of the present embodiment. First,
On the n-InP substrate 21 by MOCVD,
n-InP cladding layer 22, SCH-MQW active layer 2
3. First p-InP cladding layer 24, p-AlInA
s / p-AlGaInAs layer 25, second p-InP cladding layer 26, and p-GaInAs contact layer 2
7 is formed to form a laminated structure as shown in FIG. p-AlInAs / p-AlGaInAs layer 2
In the film formation of No. 5, first, as shown in FIG.
An InAs (for example, λg = 1.1 μm) layer 25b is formed on the first p-InP cladding layer 24, and then sequentially.
p-AlInAs layer 25a and p-AlGaInAs
The layer 25b (for example, λg = 1.1 μm) is formed.

Next, a SiO ₂ film is formed on the contact layer 27 and is patterned to form a stripe-shaped mask 33. Subsequently, using the mask 33, the contact layer 27, the second p-InP cladding layer 26, the p-AlIn
The As / p-AlGaInAs layer 25 was removed by etching, and the second p-InP cladding layer 24 was removed by etching partway, and as shown in FIG. 3 (b), the width W was 10 μm. A stripe ridge 34 is formed.

Next, the SiO used for etching is_TwoMembrane
Using the mask 33 as a mask for preventing oxidation, in steam
By performing a heat treatment at a temperature of about 500 ° C. for 90 minutes,
The p-AlInAs / p-AlGaInAs layer 25 is
Oxidation is performed from the side of the die 34 to selectively oxidize Al and Al
An oxide layer 28 is formed. Next, the SiO_TwoFilm mask 33
After the removal of SiN, SiN is_X Membrane 29
To form Next, the n-InP substrate 21 is
Polished to a thickness of about_XP on membrane 29 and window area
Mold electrode 31 and an n-side electrode 32 are formed on the back surface of the substrate, respectively.
You.

In this embodiment, Al in the laminated film in which the upper and lower surfaces of the AlInAs layer are sandwiched by the AlGaInAs layer is oxidized to form an Al oxide layer. Al which was generated at the time of implementation
The generation of voids at the interface between the oxide layer and the InP layer can be prevented. Therefore, by manufacturing the semiconductor laser device of this embodiment according to the above-described manufacturing method, the product yield of the laser device can be improved, and the reliability of the semiconductor laser device can be improved.

Embodiment 2 This embodiment is an example of the embodiment of the semiconductor laser device according to the second invention, and FIG. 8 is a sectional view showing a laminated structure of the semiconductor laser device of this embodiment. is there. The semiconductor laser device 40 according to the present embodiment has an n-type semiconductor layer having a thickness of about 100 μm.
InP substrate 41, n-InP cladding layer 42, SCH-MQW active layer 43, first p-InP cladding layer 44, p-GaI
nAsP layer 45, 0.1 μm-thick p-AlInAs layer 46, second p-InP cladding layer 47, and p-Ga
It has a laminated structure composed of the InAs contact layer 48. The p-GaInAsP layer 45 is a semiconductor layer having a composition with a band gap wavelength of 0.95 μm or more and 1.15 μm or less, for example, a band gap wavelength of 1.1 μm and a film thickness of 20 μm, and as shown in FIG. AlInAs layer 4
6 is formed in contact with the surface on the active layer side of the first p-InP
It is interposed between the cladding layer 44.

In the laminated structure, the upper part of the first p-InP clad layer 44, the p-GaInAsP layer 45, the p-A
lInAs layer 46, second p-InP cladding layer 47,
And the p-GaInAs contact layer 48 has a width of about 10
It is formed as a stripe-shaped ridge 49 of μm.
The side surface of the ridge of the p-AlInAs layer 46 is made of Al.
Is an Al oxide layer 50 selectively oxidized.

An SiN _x film 52 is formed as a protective film on the region other than the region above the ridge which is the window 51. Then, the p-side electrode 53 is formed on the SiN _x film 52 including the region of the window 51 above the ridge, and the n-side electrode 54 is formed on the n-In
Each is formed on the back surface of the P substrate.

With reference to FIG. 9, a method of manufacturing the semiconductor laser device 40 of this embodiment will be described. 9 (a) to 9 (c)
FIGS. 4A to 4C are cross-sectional views of a substrate showing a laminated structure in each step when manufacturing the semiconductor laser device of the embodiment. First, the n-InP cladding layer 42, the SCH-MQW active layer 43, the first p-InP cladding layer 44, and the p-GaIn
AsP layer 45, p-AlInAs layer 46, second p-I
An nP cladding layer 47 and a p-GaInAs contact layer 48 are formed to form a laminated structure as shown in FIG.

Next, a SiO ₂ film is formed on the contact layer 48 and patterned to form a striped mask 55. Subsequently, using the mask 55, the contact layer 48, the second p-InP cladding layer 47, the p-AlIn
The As layer 46 and the p-GaInAsP layer 45 are removed by etching, and the second p-InP cladding layer 44 is further removed by etching partway. As shown in FIG. A 10 μm striped ridge 49 is formed.

Next, the mask 55 of the SiO ₂ film used for etching is used as a mask for preventing oxidation of the p-GaInAs contact layer 48, and is subjected to a heat treatment at a temperature of about 500 ° C. for 90 minutes in water vapor to form p-GaInAs. -AlInAs
The layer 46 is oxidized from the side of the ridge 49, and Al is selectively oxidized to form an Al oxide layer 50. Next, after removing the mask 55 of the SiO ₂ film, an SiN _x film 52 is formed in a region except for the window 51 above the ridge. Then, n-InP
The substrate 41 is polished to a thickness of about 100 μm, and a p-type electrode 53 is formed on the SiN _x film 52 and the window 51 region, and an n-side electrode 54 is formed on the back surface of the substrate. Thus, the semiconductor laser device 40 shown in FIG. 8 can be formed.

In this embodiment, the p-GaInAsP layer 45 having a band gap wavelength of 1.1 μm is formed of p-AlInP.
Since it is provided in contact with the active layer side of the As layer 46, as demonstrated in the above-described experiment, the influence of the heterospike on the valence band side is reduced, and the rise of the operating voltage and the differential resistance is small. Therefore, the laser characteristics do not deteriorate during high current injection, high temperature operation, and high speed operation.

In this embodiment, the p-GaInAsP layer 45 having a band gap wavelength of 1.1 μm is formed of p-AlInP.
The p-GaInAsP layer 45 and the p-InP layer 4 are preferably provided in contact with the As layer 46 on the active layer side.
P-GaI with a band gap wavelength of 1.0 μm between
With the nAsP layer interposed, the energy on the valence band side is changed stepwise with a smaller difference. More preferably, the p-GaInAs layer 46 is p-Ga
It is better to provide the InAsP layer 45, and more desirably,
As in the case of the semiconductor laser device of Sample 1 described above, p-AlI
The p-GaInAsP layer 45 is in contact with both sides of the nAs layer 46.
And p-GaInAs having a band gap wavelength of 1.0 μm
It is better to provide a two-layer film of the P layer.

[0047]

According to the present invention, when a confinement structure is formed by an Al oxide layer formed by selectively oxidizing Al of a semiconductor layer containing Al formed on a semiconductor substrate, the Al oxide layer is directly formed of In.
When it comes into contact with a cladding layer such as a P layer, a cavity is created. Therefore, in the first invention, a semiconductor layer containing As, for example, an AlGaInAs layer or the like is present on at least one surface in the stacking direction of the semiconductor layer containing Al, so that a cavity is formed at the interface between the Al oxide film and the clad layer. To prevent it from occurring. As a result, the product yield of the semiconductor laser device can be improved, and the reliability of the semiconductor laser device can be improved.

In a semiconductor laser device having a confinement structure composed of an Al oxide layer and a semiconductor layer containing Al continuous with the Al oxide layer, different band gaps are used.
Due to the energy, a heterospike occurs at the interface between the semiconductor layer containing Al and the cladding layer, and at the time of high current injection,
This causes a decrease in laser characteristics during high-temperature operation and high-speed operation. Therefore, in the second invention, between the semiconductor layer containing Al and the cladding layer, at least the surface on the active layer side of both surfaces of the semiconductor layer containing Al is brought into contact with the valence band side of the semiconductor layer containing Al. And the semiconductor layer containing As, which has an energy on the valence band side between the energy on the valence band side and the energy on the valence band side of the cladding layer, reduces heterospikes, and reduces the operating voltage of the semiconductor laser device. (Differential resistance is reduced), and good laser characteristics are maintained during high current injection, high temperature operation, and high speed operation.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a stacked structure of a semiconductor laser device according to a first embodiment.

FIG. 2 is a cross-sectional view illustrating a configuration of a current confinement layer of the semiconductor laser device according to the first embodiment.

FIGS. 3A to 3C are substrate cross-sectional views each showing a laminated structure in each step when manufacturing the semiconductor laser device of the first embodiment.

FIG. 4 is a cross-sectional view showing a laminated structure of a conventional semiconductor laser device.

5 (a) to 5 (c) are cross-sectional views of a substrate showing a laminated structure in each step when a conventional semiconductor laser device is manufactured.

FIG. 6 is a schematic diagram showing a state in which a cavity is generated between an Al oxide layer and an InP cladding layer.

FIGS. 7A and 7B are diagrams showing a configuration of a multilayer film of a sample.

FIG. 8 is a cross-sectional view illustrating a stacked structure of the semiconductor laser device according to the second embodiment.

FIGS. 9A to 9C are substrate cross-sectional views each showing a laminated structure in each step when manufacturing the semiconductor laser device of the present embodiment.

FIG. 10 is a schematic diagram showing a band structure of a hetero junction of a p-InP layer 6, a p-AlInAs layer 5, and a p-InP layer 4.

FIGS. 11A and 11B are schematic diagrams showing a stacked structure including an AlInAs layer of the semiconductor laser devices of Sample 1 and Sample 2, respectively.

FIGS. 12A and 12B are graphs showing the relationship between the injection current and the applied voltage of the semiconductor laser devices of Sample 1 and Sample 2, respectively.

FIG. 13 is a graph showing the relationship between the injection current and the optical output of the semiconductor laser devices of Sample 1 and Sample 2.

[Explanation of symbols]

Reference Signs List 1 n-InP substrate 2 n-InP cladding layer 3 SCH-MQW active layer 4 first p-InP cladding layer 5 p-AlInAs layer 6 second p-InP cladding layer 7 p-GaInAs contact layer 8 Al oxide layer Reference Signs List 9 SiN _x film 10 p-side electrode 11 n-side electrode 12 striped ridge 13 window 14 mask 15 conventional semiconductor laser device 16 cavity 20 semiconductor laser device of first embodiment 21 n-InP substrate 22 n-InP clad layer 23 SCH -MQW active layer 24 first p-InP cladding layer 25 p-AlInAs / p-AlGaInAs layer 25 a p-AlInAs layer 25 bp p-AlGaInAs (λg = 1.1 μm) layer 26 second p-InP cladding layer 27 p-GaInAs contact layer 28 Al oxide layer 29 SiN _X film 30 windows 31 Side electrode 32 n-side electrode 33 mask 34 stripe-shaped ridge 40 semiconductor laser device 41 of embodiment 2 n-InP substrate 42 n-InP cladding layer 43 SCH-MQW active layer 44 first p-InP cladding layer 45 p- GaInAsP layer 46 p-AlInAs layer 47 second p-InP cladding layer 48 p-GaInAs contact layer 49 striped ridge 50 Al oxide layer 51 window 52 SiN _X film 53 p-side electrode 54 n-side electrode 55 mask

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeharu Yamaguchi 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Akihiko Kasukawa 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (5)

[Claims] 1. A semiconductor laser device comprising an Al oxide layer formed by selectively oxidizing Al in a semiconductor layer containing Al formed on a semiconductor substrate to form a confinement structure. When viewed in a parallel plane, it is composed of an Al oxide layer and a semiconductor layer containing Al that is continuous with the Al oxide layer. At least one surface in the stacking direction of the Al oxide layer and the semiconductor layer containing Al contains As. A semiconductor laser device having a semiconductor layer. 2. The method according to claim 1, wherein the semiconductor substrate is an InP substrate,
The semiconductor layer containing As is an AlGaInAs layer, a GaI layer.
2. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is formed of at least one of an nAsP layer, a GaInAs layer, and an InAsP layer. 3. The semiconductor device according to claim 1, wherein the semiconductor substrate is a GaAs substrate, and the cladding layer is formed of a semiconductor layer containing P.
s-containing semiconductor layer is composed of an AlGaInAs layer and an AlGaInAs layer.
2. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is formed of at least one layer of an As layer. 4. A semiconductor laser device having a confinement structure formed by an Al oxide layer formed by selectively oxidizing Al in a semiconductor layer containing Al formed on a semiconductor substrate, wherein the confinement structure is formed on the semiconductor substrate. When viewed in a parallel plane, it is composed of an Al oxide layer and a semiconductor layer containing Al which is continuous with the Al oxide layer, and is formed at least in the P-type clad layer. At least the surface on the active layer side of both surfaces of the Al-containing semiconductor layer, and has a valence band side intermediate between the valence band side energy of the Al-containing semiconductor layer and the valence band side energy of the cladding layer. A semiconductor layer having a semiconductor layer having energy of 3 nm. 5. The semiconductor substrate according to claim 1, wherein the semiconductor substrate is an InP substrate, the cladding layer is an InP layer, and the semiconductor layer containing Al is AlInAs.
The semiconductor layer containing As has a bandgap wavelength of 0.1.
GaInAsP having a composition of 95 μm or more and 1.15 μm or less
The semiconductor laser device according to claim 4, wherein the semiconductor laser device is formed of a layer.