JPH1168226A - Semiconductor laser element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve noise characteristics yield by selectively forming a high resistance region in a current path to an active layer, and by making the high resistance region from aluminum oxide in a semiconductor layer containing Al(aluminum). SOLUTION: A buffer layer 102, the first clad layer 103, a quantum well active layer 104, and the second clad layer 105 and an etch stop layer 106 are formed in sequence on a substrate 101 using the first MOCVD method. Next, the 3rd clad layer 110 and a contact layer 111 are layered using the second MOCVD method. A Si3 N4 film is formed vertically in a striped direction on the contact layer 111. The contact layer 111 is etched and a gap 112 is formed using the Si3 N4 film as a mask. Oxidizing the gap 112 forms a high resistance region 113, in which aluminum oxide in a semiconductor layer containing Al(aluminum) is formed. This maintains the reliability of a low noise laser.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly reliable and low noise semiconductor laser used for a light source of an optical disk or the like.

[0002]

2. Description of the Related Art A conventional example of a semiconductor laser (JP-A-6-85)
383) will be described. First, FIGS.
FIG. 1 shows a cross-sectional view of a conventional semiconductor laser device viewed from an end face and a cross-sectional view of a stripe in a cavity length direction, and the description will be made with reference to these drawings.

An n-GaAs buffer layer 160 is formed on an n-GaAs substrate 1601 by a first MOCVD growth method.
2. n-Al _0.55 Ga _0.45 As first cladding layer 160
3, non-doped Al _0.15 Ga _0.85 As active layer 1604,
p-Al _0.55 Ga _0.45 As second cladding layer 1605, p-Al _0.55 Ga _0.45 As
-GaAs protective layer 1606, n-Al _0.7 Ga _0.3 As current light confinement layer 1607, n-GaAs current blocking layer 16
08 is formed. n-Al _0.7 Ga _0.3 As current light confinement layer 1607, n-GaAs current blocking layer 1608
Is striped so that the width of the bottom surface is 2 μm, and the stripe groove 1609 and n-Ga
On the As current blocking layer 1608, p-Al _0.55 Ga _0.45 A
The s third cladding layer 1610 and the p-GaAs contact layer 1611 are stacked.

[0004] p-Al _0.55 G on stripe groove 1609
a _0.45 As third cladding layer 1610 and p-GaAs
After boron ions or oxygen ions are implanted into a part of the contact layer 1611, a high-temperature heat treatment (400 to 8
00 ° C.), a high resistance region 1612 is formed. The high resistance region 1612 has a size of 20 μm × 20 μm. Then, the p-GaAs cap layer 1
A p-type electrode 1613 and an n-type electrode 1614 are formed on the surface of the substrate 611 and the substrate 1601, respectively. The cavity length is set to 400 μm by cleavage. The light emitting end face is made to have a reflectance of 12% by coating with a single layer of Al ₂ O ₃ , and the opposite end face is made to have a reflectivity of 75% by coating with a multilayer film of Al ₂ O ₃ and Si.

The high resistance region 1612 has a resistance of 10 ⁴ to 10 ⁸ Ω · c.
It has a resistivity of about m, and no current is injected into the active layer immediately below. The portion of the active layer where no current is injected becomes a saturable absorption region, and self-sustained pulsation occurs. As a result, the width of the longitudinal mode spectrum of the laser light is expanded, the coherence of the laser light is reduced, and the laser light is less susceptible to noise.

[0006]

However, the above example has the following problems depending on the heat treatment temperature. First, since the heat treatment temperature is low at 400 to 650 ° C., it is difficult to completely recover crystal defects generated in the ion implantation process used for forming the high-resistance region 1612. Therefore, there is also a problem that the reliability is reduced due to the remaining defects.

On the other hand, when the heat treatment temperature is 600 ° C. to 800 ° C., diffusion of Zn as a dopant occurs, and the length of the high resistance region varies, and the desired saturable absorption amount changes, so that the characteristics vary. .

The present invention has been made to solve the above problems. In other words, a self-excited oscillation in which a high resistance region is formed in a part of the current path to the active layer, a current non-injection region is provided for the active layer, and the current non-injection region acts as a saturable absorption layer It is an object of the present invention to provide a structure of a highly reliable semiconductor laser device and a method of manufacturing the same with improved yield of noise characteristics in a low-noise semiconductor laser device.

[0009]

A semiconductor laser device according to the present invention (claim 1) is formed by selectively forming a high resistance region in a current path to an active layer and forming a current non-injection region. In the semiconductor laser device, the above object is achieved by the high resistance region being an oxide of Al formed in a semiconductor layer containing Al.

In the high resistance region, an oxide of Al (γ-Al
_{By using 2} O ₃ ), a high resistance region can be formed by heat treatment at about 400 to 600 ° C.

In the semiconductor laser device according to the present invention (claim 2), the above object is achieved by forming the high-resistance region substantially at the center of the semiconductor laser device in the resonator direction.

By forming the high-resistance region substantially at the center in the direction of the resonator, the portion of the active layer below the high-resistance region where current is not injected (saturable absorption region) is not exposed to return light. , And more stable self-excited oscillation characteristics can be obtained.

The above object is achieved by the semiconductor laser device according to the present invention (claim 3), wherein the high resistance region is formed on at least one of the resonator end faces of the semiconductor laser device.

By providing a high resistance region on the end face of the resonator, an oxide of Al (γ-Al ₂ O ₃ ) formed on the end face is provided.
Is a crystal having a high thermal conductivity, so that heat is radiated well from the end face and reliability is improved.

In the method of manufacturing a semiconductor laser device according to the present invention (claim 4), the method for manufacturing a semiconductor laser device is described in which an A is formed on a current path to an active layer.
The above object is achieved by exposing a desired region of the semiconductor layer containing l and heating it in an oxidizing atmosphere to selectively oxidize the semiconductor layer containing Al to form a high resistance region. .

The desired region of the exposed Al-containing semiconductor layer may be the end face of the resonator, or may be just above the active layer instead of the end face.

More preferably, in order for the semiconductor layer containing Al to have a sufficiently high selective oxidation ratio as compared with the other layers, it is desirable that the Al ratio be higher than the other layers. Specifically, it is desirable to be 0.9 or more.

The operation of the present invention will be described below.

In the semiconductor laser device of the present invention, the high resistance region formed by thermally oxidizing a part of the Al-containing semiconductor layer formed on the current path to the active layer at 400 to 600 ° C. Irrespective of the dopant contained in the crystal and the heat treatment temperature, it is a polycrystalline γ-Al ₂ O ₃ crystal which is thermally stable and has excellent insulating properties. Therefore, by adjusting the length of the oxidized region in the resonator direction, the amount of saturable absorption can be adjusted with good reproducibility and without being influenced by the subsequent steps. Is obtained.

Further, since no crystal defects are observed, a semiconductor laser device with no deterioration in reliability can be obtained.

Further, the effect is further clarified by the position where the high resistance region is formed in the resonator. First, when the high-resistance region is provided at the center in the direction of the resonator, the saturable absorption region (the active layer portion under the high-resistance region where current is not injected) is not exposed to return light. Without
More stable self-excited oscillation characteristics can be obtained.

When the high resistance region is provided on the end face of the resonator,
Since the oxide of Al (γ-Al ₂ O ₃ ) formed on the end face is a crystal having high thermal conductivity, heat is radiated well from the end face and reliability is improved.

Further, when the high resistance region is formed on the current path to the active layer by partially oxidizing the high Al ratio layer on the current path to the active layer and forming the high resistance region on the end face of the resonator, the selective oxidation ratio of the high Al ratio layer is changed to another. Since the size of the oxide layer is larger than that of the layer, the oxidation temperature can be reduced, and the deterioration of the oxide at a high temperature is suppressed, so that the reliability is improved. High Al
The Al ratio of the specific layer is preferably 0.9 or more in order to obtain a sufficiently high selective oxidation ratio as compared with the other layers.

[0024]

Embodiments of the present invention will be described below.

(Embodiment 1) A first embodiment will be described with reference to FIGS. In this embodiment, an example in which the present invention is applied to a self-aligned laser will be described.

The first M is formed on an n-GaAs substrate 101.
N-GaAs buffer layer 102 by OCVD growth
(Layer thickness 0.5 μm, dopant Si, carrier concentration 1 ×
10 ¹⁸ cm ⁻³ ), n-Al _0.5 Ga _0.5 As first cladding layer 103 (layer thickness 1.5 μm, dopant Si, carrier concentration 5 × 10 ¹⁷ cm ⁻³ ), quantum well active layer 104, p-type
Al _0.5 Ga _0.5 As second cladding layer 105 (layer thickness 0.3
μm, dopant Zn, carrier concentration 1 × 10 ¹⁸ c
m ⁻³ ), p-GaAs etch stop layer 106 (layer thickness 0.003 μm, dopant Zn, carrier concentration 1 × 1)
0 ¹⁸ cm ⁻³ ), n-Al _0.7 Ga _0.3 As current light confinement layer 107 (layer thickness 0.6 μm, dopant Si, carrier concentration 3 × 10 ¹⁸ cm ⁻³ ), n-GaAs current blocking layer 10
8 (layer thickness 0.3 μm, dopant Si, carrier concentration 3
× 10 ¹⁸ cm ^-3 ). A resist pattern in the form of a stripe groove having a width of 3 μm is formed on the n-GaAs current blocking layer 108, and the n-GaAs current blocking layer 108 and the n-Al _0.7 Ga _0.3 As current light confinement layer 107 are removed by etching using this as a mask. Then, a stripe groove 109 is formed. With respect to the etching, the n-GaAs current blocking layer 108 is n-A
The l _0.7 Ga _0.3 As current light confinement layer 107 is formed by an HF-based etchant. The etching is finally p-G
Stop at the aAs etch stop layer 106.

Next, the resist is removed, and the second MOC
According to the VD method, p-
Al _0.5 Ga _0.5 As third cladding layer 110 (layer thickness 1.2
μm, dopant Zn, carrier concentration 3 × 10 ¹⁸ c
m ^-3 ), p-GaAs contact layer 111 (layer thickness 1.0
μm, dopant Zn, carrier concentration 1 × 10 ²⁰ c
m ⁻³ ) is formed by lamination.

Next, the p-GaAs contact layer 111
An Si ₃ N ₄ film having a width of 250 μm is formed on the upper surface at an interval of 50 μm perpendicular to the stripe direction. Using this as a mask, the p-GaAs contact layer 111 is etched to form the groove 1
12 is formed. The wafer thus manufactured is heated at 400 to 600 ° C. in steam generated by bubbling nitrogen gas by heating pure water to about 80 ° C. to perform thermal oxidation. Here, the test was performed at 470 ° C. for 60 minutes. As shown in FIG. 2, a portion of the p-third cladding layer 110 is oxidized from the groove 112 to form a high-resistance (oxidized) region 113. The oxidation rate is proportional to the Al ratio, and GaAs not containing Al is hardly oxidized. Therefore, the oxidation does not include Al.
Stop at the GaAs current blocking layer 108 and the p-GaAs etch stop layer 106.

When the thermal oxidation temperature is lower than 400 ° C., the oxidation rate is reduced, and it takes several hours to obtain a desired oxidized region. When the thermal oxidation temperature is higher than 600 ° C., the element life is deteriorated.

[0030] Then, to remove the Si ₃ N ₄ film, forming a growth layer and the outer surface and on the p-type electrode 114, n-type electrode 115 respectively on the outer surface of the substrate 101 of the high resistance region 113, ^10-5 Anneal at 450 ° C. for 2 minutes in a vacuum of about Torr. Cleavage is performed such that the cleavage end face is located at a distance of 100 μm from both ends of the high resistance region 113 in the resonator direction. (The resonator length of the element is 250 μm.) The light output end face is made to have a reflectivity of 30% by coating with a single layer of Al ₂ O ₃ , and the opposite end face is made to have a reflectivity of 75% by being coated with a multilayer film of Al ₂ O ₃ and Si. .

FIG. 3 shows the wavelength spectrum of the device of this embodiment at an optical output of 5 mW, and FIG. 4 shows the relative noise intensity characteristics with respect to the amount of return light. The relative noise intensity characteristics are shown for the maximum value and the minimum value. 3 and 4, in the present embodiment, the longitudinal mode clearly becomes multi-mode due to the effect of the saturable absorption and self-excited vibration occurs, the difference between the minimum value and the maximum value of the relative noise intensity is small, and the return light amount is reduced. On the other hand, there was not much change,
It can be seen that coherent noise is suppressed. The maximum relative noise intensity is -140d when the amount of return light is between 0.1 and 10%.
B / Hz is obtained.

The reliability of this example and a comparative example in which the high-resistance region 115 was formed by heat treatment (600 ° C.) after oxygen ion implantation was evaluated. The running conditions were 70 ° C., 5 mW, and 20 runs each. 5 (a) and 5 (b) show the aging characteristics of the present example and the comparative example, respectively, up to 1000 hours. In the present embodiment, all of the 20 vehicles are traveling stably, whereas in the conventional example, sudden death or a significant decrease in light output was observed by 200 hours.

Table 1 shows the results of the device life.

[0034]

[Table 1]

When the variation of the maximum relative noise intensity was evaluated with respect to the present example and the comparative example using 50 elements, the results shown in FIGS. 6A and 6B were obtained. In the present embodiment, the distribution is in the range of -140 to -145 dB / Hz.
The distribution was between 10 and -145 dB / Hz. Also,
When the variation in the threshold current was examined, almost no variation was observed in the example, but in the comparative example having a large variation in the maximum relative noise intensity, a large variation also occurred in the threshold current.

The quantum well active layer 104 in the present embodiment is non-doped, and has a quantum well structure in which three pairs of Al _0.11 Ga _0.89 As well layers (layer thickness: 80 °) and Al _0.35 Ga _0.65 As barrier layers (layer thickness: 80 °) are stacked. And an Al _0.35 Ga _0.65 As optical guide layer sandwiching both sides of the quantum well structure (layer thickness 2
50 °).

In the above embodiment, the quantum well layer is used as the active layer. However, the effects of the present invention can be obtained by using a low mixed crystal AlGaAs bulk crystal.

(Embodiment 2) Referring to FIG. 7 and FIG.
An example will be described. In this embodiment, an example in which the present invention is applied to a ridge type laser will be described.

A first M is formed on an n-GaAs substrate 701.
N-GaAs buffer layer 702 by OCVD growth
(Layer thickness 0.5 μm, dopant Si, carrier concentration 1 ×
10 ¹⁸ cm ⁻³ ), n-Al _0.5 Ga _0.5 As first cladding layer 703 (layer thickness 1.5 μm, dopant Si, carrier concentration 5 × 10 ¹⁷ cm ⁻³ ), quantum well active layer 704, p-
Al _0.5 Ga _0.5 As second cladding layer 705 (layer thickness 0.3
μm, dopant Zn, carrier concentration 1 × 10 ¹⁸ c
m ^-3 ), p-GaAs etch stop layer 706 (layer thickness 0.003 μm, dopant Zn, carrier concentration 1 × 1)
0 ¹⁸ cm ⁻³ ), a p-Al _0.5 Ga _0.5 As third cladding layer 707 (layer thickness 0.9 μm, dopant Zn, carrier concentration 3 × 10 ¹⁸ cm ⁻³ ) is grown, and the p-GaAs cap layer 708 ( A layer thickness of 0.7 μm, a dopant Zn, and a carrier concentration of 3 × 10 ¹⁸ cm ⁻³ ) are formed. P-cap layer 70 using the striped resist pattern as a mask
8 is processed into a convex stripe (upper surface width 2.0 μm). The p-third cladding layer 707 is processed into a ridge stripe (bottom width 2.0 μm) using the p-cap layer 708 processed into a stripe as a mask.

At this time, etching around the ridge stripe is stopped by the etch stop layer 706. Then, the resist is removed.

Next, n-Al _0.7 Ga _0.3 As is formed by filling the periphery of the ridge by the second MOCVD growth method.
Current-light confinement layer 709 (layer thickness 0.6 μm, dopant Si, carrier concentration 3 × 10 ¹⁸ cm ⁻³ ), n-GaAs
Current blocking layer 710 (layer thickness 0.6 μm, dopant Si,
An unnecessary layer grown directly on the p-GaAs cap layer 708 with a carrier concentration of 3 × 10 ¹⁸ cm ⁻³ ) is removed by etching, and the thickness of the p-GaAs cap layer 708 is adjusted to 0.3 μm. p-GaAs contact layer 711 (layer thickness 1
μm, dopant Zn, 1 × 10 ¹⁹ cm ⁻³ ) are formed by lamination by the third MOCVD growth method.

Next, the p-GaAs contact layer 711
An Si ₃ N ₄ film having a width of 250 μm is formed on the upper surface at an interval of 50 μm perpendicular to the stripe direction. Using this as a mask, the p-GaAs contact layer 711 is etched to form a groove 7.
12 is formed. The wafer thus manufactured is heated at 400 to 600 ° C. in steam generated by bubbling nitrogen gas by heating pure water to about 80 ° C. to perform thermal oxidation. Here, the test was performed at 470 ° C. for 60 minutes. As shown in FIG. 8, a part of the p-third cladding layer 707 is oxidized from the groove 712 to form a high-resistance (oxidized) region 713. The oxidation rate is proportional to the Al ratio, and GaAs not containing Al is hardly oxidized. Therefore, the oxidation does not include Al.
Stop at the GaAs current blocking layer 710 and the p-GaAs etch stop layer 706.

When the thermal oxidation temperature was lower than 400.degree. C., the oxidation rate was lowered, and it took several hours to obtain a desired high resistance region. When the thermal oxidation temperature was higher than 600.degree. C., the life of the element was deteriorated.

[0044] Then, to remove the Si ₃ N ₄ film, forming a growth layer and the outer surface and on the p-type electrode 714, n-type electrode 715 respectively on the outer surface of the substrate 701 of the high resistance region 713, ^10-5 Anneal at 450 ° C. for 2 minutes in a vacuum of about Torr. 100 from the groove 712 toward the resonator.
Cleavage is performed so that the cleavage end face is located at a distance of μm.
(The resonator length of the element is 250 μm.) The light emitting end face is the cleavage end face side, the end face of which is 30% by Al ₂ O ₃ single layer coating, and the opposite dry etching end face is Al ₂ O ₃ . A 75% reflective film is formed by multi-layer Si coating.

FIG. 9 shows the wavelength spectrum of the device of this embodiment at an optical output of 5 mW, and FIG. 10 shows the relative noise intensity characteristics with respect to the amount of return light. The relative noise intensity characteristics are shown for the maximum value and the minimum value.

From FIGS. 9 and 10, in this embodiment, the longitudinal mode clearly becomes multi-mode due to the effect of saturable absorption, and self-excited vibration occurs, and the difference between the minimum value and the maximum value of the relative noise intensity is small. It can be seen that there is little change in the amount of return light, and coherent noise is suppressed. Return light amount is 0.1
Maximum relative noise intensity between-10% and -140dB / Hz
Have gained.

The reliability of this example and a comparative example in which the high-resistance region 715 was formed by heat treatment after oxygen ion implantation was evaluated. Running conditions: 70 ° C, 5m
W was performed with 20 pieces each. 11 (a) and 11 (b) show the aging characteristics of the present example and the comparative example, respectively, up to 1000 hours. In this embodiment, 20
While all the vehicles are running stably, in the conventional example, 20
By 0 hr, sudden death or a significant decrease in light output was observed.

Table 2 below shows the results of the device life.

[0049]

[Table 2]

In the present embodiment and the comparative example, the variation of the maximum relative noise intensity was small, and was -135 to -145.
It was distributed between dB / Hz.

(Embodiment 3) A description will be given with reference to FIGS. In the present embodiment, an example is shown in which the high resistance region in the second embodiment is formed on the end face of the resonator.

An n-GaAs buffer layer 120 is formed on an n-GaAs substrate 1201 by the first MOCVD growth method.
2 (layer thickness 0.5 μm, dopant Si, carrier concentration 1
× 10 ¹⁸ cm ⁻³ ), n-Al _0.5 Ga _0.5 As first cladding layer 1203 (layer thickness 1.5 μm, dopant Si, carrier concentration 5 × 10 ¹⁷ cm ⁻³ ), quantum well active layer 120
4. p-Al _0.5 Ga _0.5 As second cladding layer 1205
(Layer thickness 0.3 μm, dopant Zn, carrier concentration 1 ×
10 ¹⁸ cm ^-3 ), p-GaAs etch stop layer 120
6 (layer thickness 0.003 μm, dopant Zn, carrier concentration 1 × 10 ¹⁸ cm ⁻³ ), p-Al _0.5 Ga _0.5 As third cladding layer 1207 (layer thickness 0.9 μm, dopant Zn,
A carrier concentration of 3 × 10 ¹⁸ cm ⁻³ ) is grown, and p-GaAs is grown.
s cap layer 1208 (layer thickness 0.7 μm, dopant Z
n, a carrier concentration of 3 × 10 ¹⁸ cm ⁻³ ) is formed.

The p-cap layer 1208 is processed into a convex stripe (upper surface width: 2.0 μm) using the stripe resist pattern as a mask. P processed into a stripe
Processing the p-third cladding layer 1207 into a ridge stripe (bottom width 2.0 μm) using the cap layer 1208 as a mask.

At this time, etching around the ridge stripe is stopped by the etch stop layer 1206. Then, the resist is removed.

Next, n-Al _0.7 Ga _0.3 As is formed so as to fill the ridge periphery by the second MOCVD growth method.
Current-light confinement layer 1209 (layer thickness 0.6 μm, dopant Si, carrier concentration 3 × 10 ¹⁸ cm ⁻³ ), n-GaAs
s current blocking layer 1210 (layer thickness 0.6 μm, dopant S
i, a carrier concentration of 3 × 10 ¹⁸ cm ⁻³ ), an unnecessary layer grown immediately above the p-GaAs cap layer 1208 is removed by etching, and the p-GaAs cap layer 1208 is removed by 0.3.
Adjust to a thickness of μm. p-GaAs contact layer 121
1 (layer thickness 1 μm, dopant Zn, 1 × 10 ¹⁹ cm ⁻³ )
Is formed by a third MOCVD growth method.

On the p-GaAs contact layer 1211, 250 μm-wide Si ₃ N ₄ films are formed at 10 μm intervals perpendicular to the stripe direction. Using this as a mask, n-G by reactive ion beam etching using chlorine gas
The growth layer is etched until it reaches the aAs substrate 1201.

At this time, the side surface of the formed groove 1212 is made to be a mirror surface and is used as a resonator end surface.

The wafer thus manufactured is heated at 400 ° C. to 600 ° C. in steam generated by heating pure water to about 80 ° C. and bubbling nitrogen gas to perform thermal oxidation.

Here, the reaction was performed at 500 ° C. for 15 minutes. At this time, as shown in the cross-sectional view of the center of the ridge in the resonator direction in FIG. 13, the side surface of the groove 1212 is oxidized, and a high-resistance (oxidized) region 1213 is formed near the end surface. Since the length of the oxidized region of each layer varies depending on the Al ratio, it is defined by the length of the oxidized region of the layer having the highest Al ratio among the layers serving as current paths.

In this embodiment, the layers having a high Al ratio among the layers forming the current path are the first to third cladding layers (the Al ratio is commonly 0.5), and the length of the oxidized region in the same layer is reduced. The length is set to the length of the high resistance region 1213. Here, the thickness was 25 μm.

Next, the Si ₃ N ₄ film is removed, and the p-type electrode 1 is formed on the outer surface of the growth layer and the outer surface of the substrate 1201, respectively.
214, an n-type electrode 1215 is formed, and annealing is performed at 450 ° C. for 2 minutes in a vacuum of about 10 ⁻⁵ Torr. Groove 12
12, the light-emitting end face is 30% coated with a single layer of Al ₂ O ₃ and the opposite end face is Al ₂
A multilayer coating of O ₃ and Si results in a reflectance of 75%. The bar is made into chips.

The return light quantity of the element of this embodiment is 0.1 to 10
%, The maximum relative noise intensity at a light output of 3 mW is -142.
dB / Hz, and good noise characteristics are obtained. In addition, 20 elements were separated and running conditions were 70 ° C and 5m
The reliability was evaluated as W. All 20 pieces run stably, and a device life of 10,000 hours or more is obtained.

(Embodiment 4) A description will be given with reference to FIGS. In the present embodiment, an example is shown in which a high resistance region is formed by oxidizing a high Al ratio layer serving as a selective oxidation layer on the end face of the resonator in the second embodiment.

An n-GaAs buffer layer 140 is formed on an n-GaAs substrate 1401 by the first MOCVD growth method.
2 (layer thickness 0.5 μm, dopant Si, carrier concentration 1
× 10 ¹⁸ cm ⁻³ ), n-Al _0.5 Ga _0.5 As first cladding layer 1403 (layer thickness 1.5 μm, dopant Si, carrier concentration 5 × 10 ¹⁷ cm ⁻³ ), quantum well active layer 140
4. p-Al _0.5 Ga _0.5 As second cladding layer 1405
(Layer thickness 0.3 μm, dopant Zn, carrier concentration 1 ×
10 ¹⁸ cm ⁻³ ), p-Al _0.9 Ga _0.1 As selective oxidation layer 1
406, p-GaAs etch stop layer 1407 (layer thickness 0.003 μm, dopant Zn, carrier concentration 1 × 1
0 ¹⁸ cm ^-3 ), a third cladding layer 1408 of p-Al _0.5 Ga _0.5 As (layer thickness 0.9 μm, dopant Zn, carrier concentration 3 × 10 ¹⁸ cm ^-3 ), and a p-GaAs cap layer 1409 ( A layer thickness of 0.7 μm, a dopant Zn, and a carrier concentration of 3 × 10 ¹⁸ cm ⁻³ ) are formed.

The p-cap layer 1409 is processed into a convex stripe (upper surface width: 2.0 μm) using the stripe resist pattern as a mask. P processed into a stripe
Process the p-third cladding layer 1408 into a ridge stripe (bottom width 2.0 μm) using the cap layer 1409 as a mask.

At this time, the etching is stopped by the etch stop layer 1407 around the ridge stripe. Then, the resist is removed.

Next, n-Al _0.7 Ga _0.3 As is formed by filling the periphery of the ridge by the second MOCVD growth method.
Current-light confinement layer 1410 (layer thickness 0.6 μm, dopant Si, carrier concentration 3 × 10 ¹⁸ cm ⁻³ ), n-GaAs
s current blocking layer 1411 (layer thickness 0.6 μm, dopant S
i, the carrier concentration is 3 × 10 ¹⁸ cm ⁻³ ), the unnecessary layer grown on the p-cap layer 1409 is removed by etching, and the thickness of the p-cap layer 1409 is adjusted to 0.3 μm.

A p-GaAs contact layer 1412 (layer thickness 1 μm, dopant Zn, 1 × 10 ¹⁹ cm ⁻³ ) is formed by a third MOCVD growth method.

On the p-GaAs contact layer 1412, Si ₃ N ₄ films having a width of 250 μm are formed perpendicularly to the stripe direction at intervals of 10 μm. Using this as a mask, n-G by reactive ion beam etching using chlorine gas
The growth layer is etched until it reaches the aAs substrate 1401.

At this time, the side surface of the formed groove 1413 is made to be a mirror surface, and is used as a resonator end surface. The wafer thus prepared is heated in pure water to about 80 ° C., and bubbling with nitrogen gas.
Thermal oxidation is performed by heating at 600 ° C.

Here, the test was performed at 400 ° C. for 5 minutes. At this time, the selective oxidation layer 1409 is oxidized from the groove 1413 as shown in the cross-sectional view of the center of the ridge in the resonator direction in FIG. 15, and a high resistance (oxidized) region 1414 is formed near the end face. Each layer other than the selective oxidation layer 1406 exposed in the groove 1413 is hardly oxidized because the Al ratio is smaller, the oxidation temperature is lower, and the oxidation time is shorter than that of the same layer. Note that the length of the high resistance region 1413 was 25 μm.

Next, the Si ₃ N ₄ film is removed, and the p-type electrode 1 is formed on the outer surface of the growth layer and the outer surface of the substrate 1401, respectively.
415, an n-type electrode 1416 are formed, and annealing is performed at 450 ° C. for 2 minutes in a vacuum of about 10 ⁻⁵ Torr. Groove 14
13, the light-emitting end face is 30% by Al ₂ O ₃ single-layer film coating, and the opposite end face is Al ₂
A multilayer coating of O ₃ and Si results in a reflectance of 75%. The bar is made into chips.

The return light quantity of the element of this embodiment is 0.1 to 10
%, The maximum relative noise intensity at a light output of 3 mW is -142.
dB / Hz, and good noise characteristics are obtained. In addition, 20 elements were selected, and running conditions were 70 ° C., 5
The reliability was evaluated as mW. All 20 pieces stably run, and the element life of 20,000 hr or more was obtained.

The present invention is not limited to the above-described embodiments, but can be applied to other layer thicknesses, Al mixed crystal ratios, and carrier concentrations as long as the effects of the present invention are obtained.

In addition to the MOCVD method, the effects of the present invention can be obtained by MBE (molecular beam epitaxy), LPE (liquid phase epitaxy), MOMBE, and ALE (atomic beam epitaxy). As long as it is applicable.

Although the present invention has been described with respect to the application to AlGaAs / GaAs-based materials, the present invention is also applicable to other materials.
The same applies to GaInP / GaAs-based materials.

[0077]

According to the semiconductor laser device of the present invention, Al on a stripe portion which is a current injection path sandwiched between current constriction layers is formed.
A high resistance region is formed by thermally oxidizing a part of the semiconductor layer including the semiconductor layer, and a current non-injection region is formed in the active layer. As a result, a self-sustained pulsation type low-noise laser that is effective in applications such as optical disks can be obtained with good reproducibility while maintaining reliability.

Further, by forming the high resistance region at the center or end face of the resonator, the saturable absorption amount can be provided stably and with good controllability, and the characteristic yield can be improved.

In the case where the high resistance region is formed at the end face portion, by thermally oxidizing a part of the high Al ratio layer, the oxidation temperature can be reduced and the reliability can be further improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a semiconductor laser device according to a first embodiment of the present invention.

FIG. 2 is a center sectional view of a stripe portion in a resonator direction of the semiconductor laser device according to the first embodiment of the present invention;

FIG. 3 is a wavelength spectrum of the semiconductor laser device according to the first embodiment of the present invention.

FIG. 4 shows a relative noise intensity characteristic with respect to a return light amount of the semiconductor laser device according to the first embodiment of the present invention.

FIG. 5A shows an aging characteristic of the semiconductor laser device according to the first embodiment of the present invention, and FIG. 5B shows an aging characteristic of the conventional semiconductor laser device.

FIG. 6A is a diagram showing a distribution of relative noise intensity of the semiconductor laser device according to the first embodiment of the present invention, and FIG.
FIG. 4 is a diagram showing a distribution of relative noise intensity of a conventional semiconductor laser device.

FIG. 7 is a sectional view showing a semiconductor laser device according to a second embodiment of the present invention.

FIG. 8 is a center cross-sectional view of a ridge portion in a resonator direction of a semiconductor laser device according to a second embodiment of the present invention.

FIG. 9 is a wavelength spectrum of the semiconductor laser device according to the second embodiment of the present invention.

FIG. 10 is a diagram showing a relative noise intensity characteristic with respect to a return light amount of a semiconductor laser device according to a second embodiment of the present invention.

FIG. 11 is a diagram showing aging characteristics of a semiconductor laser device according to a second embodiment of the present invention.

FIG. 12 is a sectional view showing a semiconductor laser device according to a third embodiment of the present invention.

FIG. 13 is a center sectional view of a stripe portion in a resonator direction showing a semiconductor laser device according to a third embodiment of the present invention;

FIG. 14 is a sectional view showing a semiconductor laser device according to a fourth embodiment of the present invention.

FIG. 15 is a center sectional view of a ridge portion in a resonator direction showing a semiconductor laser device according to a fourth embodiment of the present invention.

FIG. 16 is a cross-sectional view showing a conventional semiconductor laser device.

FIG. 17 is a center sectional view of a stripe portion in a resonator direction showing a semiconductor laser device of a conventional example.

[Explanation of symbols]

1, 101, 701, 1201, 1401, 1601
n-substrate 2, 102, 702, 1202, 1402, 1602
Buffer layer 3, 103, 703, 1203, 1403, 1603
n-first cladding layer 4, 104, 704, 1204, 1404, 1604
Quantum well active layer 5, 105, 705, 1205, 1405, 1605
p-second cladding layer 6, 1406 p-AlGaAs selective oxidation layer 7, 106, 706, 1206, 1407, 1606
Etch stop layer 8, 107, 709, 1209, 1410, 1607
Current-light confinement layer 9, 108, 710, 1210, 1411, 1608
n-GaAs current blocking layer 10, 708, 1208, 1409 p-GaAs cap layer 11, 109, 1609 stripe groove 12, 110, 707, 1207, 1408, 1610
p-third cladding layer 13, 111, 711, 1211, 1412, 1611
p-GaAs contact layer 14, 112, 712, 1212, 1413 Groove 15, 113, 713, 1213, 1414, 1612
High resistance region 16, 114, 714, 1214, 1415, 1613
p-side electrode 17, 115, 715, 1214, 1416, 1614
n-side electrode

Claims (4)

[Claims] 1. A semiconductor laser device in which a high resistance region is selectively formed in a current path to an active layer to form a current non-injection region, wherein the high resistance region is formed in a semiconductor layer containing Al. Al
A semiconductor laser device characterized by being an oxide of: 2. The semiconductor laser device according to claim 1, wherein said high-resistance region is formed substantially at a center of said semiconductor laser device in a cavity direction. 3. The semiconductor laser device according to claim 1, wherein the high resistance region is formed on at least one of the cavity end faces of the semiconductor laser device. 4. An Al-containing semiconductor layer formed on a current path to an active layer is exposed in a desired region and heated in an oxidizing atmosphere to selectively oxidize the Al-containing semiconductor layer. 4. The method for manufacturing a semiconductor laser device according to claim 1, wherein a high resistance region is formed.