WO2005104318A1

WO2005104318A1 - Semiconductor light-emitting device

Info

Publication number: WO2005104318A1
Application number: PCT/JP2005/008327
Authority: WO
Inventors: Kenji Shimoyama; Takashi Fukada; Yoji Tokumitsu; Nobuhiro Arai; Kaori Kurihara
Original assignee: Mitsubishi Chemical Corporation
Priority date: 2004-04-23
Filing date: 2005-04-25
Publication date: 2005-11-03
Also published as: TW200610188A

Abstract

A semiconductor light-emitting device having a low element resistance, a low thermal resistance, a low passage resistance and a small operating current and capable of high output operation is characterized in that it comprises a substrate, a first-conductivity-type clad layer, an active layer, a second-conductivity-type first clad layer, a second-conductivity-type second clad layer having a stripe ridge structure, a current block layer so formed on the second-conductivity-type first clad layer as to sandwich the ridge, and a second-conductivity-type third clad layer formed on the ridge of the second-conductivity-type second clad layer and the current block layer in the vicinity of the ridge, all formed sequentially on the substrate and in that the cross section of the ridge perpendicular to the longitudinal direction of the stripe of the ridge structure is a trapezoid satisfying the following relation. 0.05<h/[(a+b)/2]<0.5 (h is the height of the cross section, a is the upper base of the cross section, and b is the lower base of the cross section).

Description

Specification

Semiconductor light emitting device

Technical field .

The present invention relates to a semiconductor light emitting device useful as a semiconductor laser or the like, and more particularly to a semiconductor light emitting device having a low element resistance and capable of high output operation. Such semiconductor light emitting devices include semiconductor laser devices capable of self-sustained pulsation. Background art

(1) Conventional technology for semiconductor light emitting devices

2. Description of the Related Art In recent years, laser diodes (LD) using III-V group semiconductor materials have been actively developed as light sources for information processing devices such as compact disks and optical disks. As an example of a conventional LD using an III-V compound semiconductor material, there is an LD made of an A1GaInP-based compound semiconductor having a structure schematically shown in FIG. In FIG. 7, 401 is an n-type substrate, 402 is an n-type first cladding layer, 403 is an active layer, 404 is a p-type second cladding layer, and 405 is a p-type etching stop. Layer, 406 is a p-type third cladding layer with a ridge structure, 407 is an n-type current blocking layer, 408 is a p-type contact layer, 409 is a p-side electrode, and 410 is an n-side Electrodes. In the LD using the conventional A1GaInP-based semiconductor material shown in Fig. 7 (hereinafter referred to as "conventional type DJ"), the p-type third cladding layer 406 is sandwiched between the current blocking layers 407. The p-type third cladding layer 406 has a structure in which the current is confined at the ridge portion, and thus generally has high pass resistance, thermal resistance, and element resistance. However, there have been problems such as an increase in the amount of heat generated, a decrease in optical output due to thermal saturation, an increase in operating current when operated at a temperature higher than room temperature, and a difficulty in applying high frequency superposition.

In the conventional LD, zinc was used as a p-type impurity in the p-type cladding layers 404 and 406. Zinc has a property of being easily diffused in the A1GaInP crystal, and therefore, zinc in the p-type cladding layer during repeated epitaxial growth. It often occurred that lead diffused into the active layer. When the sub-layers and diffuse into the active layer in this manner, the crystallinity of the active layer deteriorates and the life is shortened. On the other hand, if the zinc concentration is reduced to prevent diffusion, the operating voltage increases and laser oscillation becomes difficult.

Furthermore, in conventional LDs, the n-type cladding layer and the p-type cladding layer have a double heterostructure with a larger A1 composition than the active layer in order to confine the emitted light in the active layer. . However, if the amount of A1 in the P-type cladding layer is increased to enhance light confinement, for example, the carrier concentration decreases, and as a result, the device resistance increases and the driving current increases. there were. On the other hand, if the amount of A 1 in the p-type cladding layer is reduced in order to lower the drive current, light confinement and carrier confinement are weakened, and the luminous efficiency is degraded.

Several semiconductor light emitting devices have been developed to solve the above problem. For example, Japanese Unexamined Patent Application Publication No. 7-2974833 discloses a semiconductor laser having a highly doped p-type second cladding layer (ridge: current constriction portion) in order to reduce device resistance. Has been described. However, there is a disadvantage in that a P-type dopant such as zinc diffuses into the active layer during epitaxy growth or during energization, leading to deterioration of device characteristics and reliability. On the other hand, Japanese Patent Application Laid-Open No. H11-26880 discloses that a p-type second cladding layer (ridge: current constriction part) and an active layer are formed in order to prevent diffusion of a p-type dopant into the active layer. Discloses a semiconductor laser device provided with a carrier diffusion suppressing layer. However, the carrier diffusion suppressing layer described in the publication cannot sufficiently cope with a change in the diffusion state of the P-type dopant due to the growth temperature, crystallinity, etc., and further has a variation in element characteristics and a problem in reproducibility of reliability. was there. Furthermore, Japanese Patent Application Laid-Open No. 11-878332 discloses that a p-type cladding layer and an active layer are provided between a p-type cladding layer and an active layer in order to prevent diffusion of a p-type dopant into the active layer. A semiconductor laser having a layer with a pan gap between the layer and the layer is described. However, in this semiconductor laser, the etching process of the ridge portion is complicated, and the etching is difficult. There is a drawback that it is more difficult to form a stable ridge shape, for example, a depression is formed on the upper side of the ridge portion.

On the other hand, the hereditary LD normally controls the fundamental transverse mode by forming a stripe-shaped ridge in the [—110] direction (Fujii et al., Electronics Letters Vol. 23, No. 18). No. 938-9339). By selecting the stripe direction of the ridge in the [111] direction, the luminous efficiency of the active layer composed of A1GaInP ordered crystal is improved compared to the [110] direction, and the threshold current density is increased. This is because it can be reduced. In order to perform the basic transverse mode with higher power, it is necessary to make the ridge width narrower and the height of the ridge higher, and in the [110] direction, a large ridge inside the ridge is required. There was a problem that heat was generated.

In order to solve the above problem in the ridge formation direction,

A semiconductor laser formed in the [110] direction has been developed so far (Japanese Patent Laid-Open No. 7-193313). However, the ridge structure described in this publication has an inverted mesa shape, and it is necessary to perform high-temperature growth (700 to 850 ° C.) in a disordered state in order to form the inverted mesa-shaped p-type third cladding layer. is there. If grown at a high temperature in order to bring the disorder, the p-type dopant diffuses into the active layer during the growth process, and the crystallinity of the active layer deteriorates, the life is shortened, and the reliability is reduced. .

It is desired to solve the above-mentioned problems of the prior art and to provide a semiconductor light emitting device capable of operating at a high output with low element resistance, thermal resistance, passing resistance, and operating current. No semiconductor light emitting device has been provided so far. (2) Conventional technology for semiconductor laser devices capable of self-pulsation

Among the semiconductor light emitting devices, a conventional technology relating to a semiconductor laser device capable of self-sustained pulsation is described below. -A self-sustained pulsation type semiconductor laser (wavelength multimode) that is resistant to optical noise from the optical disk is suitable as a light source for reading the optical disk. Conventionally, as a self-pulsation type semiconductor laser, an inner stripe type laser using a semiconductor current block layer as shown in FIGS. 8 (a) and 8 (b) has been used. Structure without light absorption layer In the structure, self-sustained pulsation is usually achieved by forming a saturable absorption region inside the active layer. The saturable absorption region can be formed on both sides immediately below the ridge or group as shown in FIGS. 8 (a) and 8 (b) by expanding the light distribution more than the current injection region. In this supersaturated absorption region, the generation (emission) of carriers and the extinction (extinction) of carriers are repeated in a short time cycle, so that the vertical mode becomes multi (wavelength multimode), and low noise can be realized. In order to reduce the return light noise of this semiconductor laser device, a method of performing longitudinal multi-mode oscillation using the self-excited oscillation phenomenon of the semiconductor laser has been developed. For example, Japanese Patent Application Laid-Open No. 63-202083 discloses the details. Is described.

Recently, in order to improve the recording density mainly for digital video discs, instead of the conventional A 1 Ga As (wavelength around 780 nm) as a light source for information processing, the visible ( (Usually in the 630 to 69 Onm band) Lasers have begun to be put into practical use. A conventional semiconductor laser diode (LD) using an A 1 G a In P semiconductor material—for example, one having a structure schematically shown in FIG.

In FIG. 9, reference numeral 601 denotes an n-type GaAs substrate; 602, a cladding layer made of n-type A1GaInP formed on the substrate 601; 603, an active layer made of A1GaInP. Reference numeral 604 denotes a cladding layer made of p-type A1GaInP, 605 denotes a current blocking (blocking) layer made of n-type GaAs, and 606 denotes a contact layer. Here, the mixed crystal ratio is set so that the energy gap of the A1GaInP active layer 603 is smaller than the energy gap of the A1GaInP clad layers 602 and 604. It has a hetero structure. The current blocking layer 605 is provided for the purpose of performing a so-called current confinement in order to obtain a current density required for laser oscillation. The current blocking layer 605 is formed by selectively etching the layer 604 to form a ridge and then selectively growing it using an amorphous film such as SiNX.

In conventional A 1 GaAs-based lasers (wavelength around 78 Onm), low noise is realized by the CSP structure, V-SIS structure, SAS structure, and the like. For example, in Toshiba Review Vol. 40, No. 7, Paragraphs 576-578, the current constriction causes A stripe for current injection is formed, and a saturable absorber region is formed on the 層 side of the stripe in the active layer. As a result, laser oscillation starts and stops repeatedly, that is, self-excited oscillation is caused by the oscillation of the refractive index of the light emitting portion due to the interaction between light and carriers in the active layer.

However, the method of forming a saturable absorber in the active layer is applied to a visible (usually 60-690 nm band) laser using a conventional A1GaInP system as shown in FIG. Current spread in the p-cladding layer region immediately below the current block layer increases the function as a saturable absorber due to excessive carrier injection, and realizes stable self-sustained pulsation up to the high-temperature region. 1 Difficulties 1 In the autumn of 1994, Japan Society of Applied Physics Academic Lectures 20 0 p _ S—15, in the Spring of 1995 Joint Lectures on Applied Physics, 2 8 a— ZG _ 9 It has been reported. Thus, as shown in FIG. 10, an A1GaInP-based self-excited oscillation laser provided with a saturable absorption layer having a band gap similar to that of oscillation light outside the active layer is disclosed in Japanese Patent Application Laid-Open No. 7-26363. H. Adachi, et al. Self-sustained pulsation in 650 nm-band AlGalnP visible laser diode with highly doped suturable absorbing layer, IEEE Photon. Technol. Lett. 7, pl406 1995), self-oscillation is 60. It has been confirmed up to the high temperature of C. However, in the method of inserting a saturable absorption layer, a steep transition of the optical output is observed at the rise of oscillation as shown in Fig. 11. For this reason, when controlling the laser output to be constant by incorporating it into an optical disk drive device, if automatic power control (APC) is used in a low output area, the APC circuit will oscillate and power control will not be possible Problem may occur. Furthermore, by using a saturable absorption layer, oscillation in the saturable absorption region may be lost, and the value current may be significantly increased. Since the thickness largely depends on the distance between the absorption layer and the active layer, reproducibility and uniformity are strictly required, and the yield tends to be low.

Visible light using an A 1 G a In P system with a saturable absorption layer (normally To overcome the practical problem of self-pulsation lasers, supersaturation in the active layer is the same as in the case of conventional A1GaAs-based lasers (wavelength around 780 nm). It is considered desirable to realize stable self-sustained pulsation up to the high-temperature region by a method of stably forming the absorber.

However, in the LD using the conventional AlGaInP semiconductor material (hereinafter referred to as “conventional LD”) shown in FIG. 12, the p-type third cladding layer 906 is composed of the current blocking layer 906. 7, and has a structure in which the current is confined at the ridge portion of the P-type third cladding layer 906, and thus generally has high passing resistance, thermal resistance, and element resistance. Therefore, in the conventional LD, the amount of heat generated by the element at the time of high power injection increases, the temperature of the active layer rises, and self-sustained pulsation becomes difficult to occur. There were problems such as difficulty.

In the conventional LD, zinc is used as a p-type impurity in the p-type cladding layers 904 and 906. Since zinc is easily diffused in AlGaInP crystals, zinc in the p-type cladding layer diffuses into the active layer during repeated epitaxial growth. Often occurs. When zinc diffuses into the active layer in this manner, the crystallinity of the active layer is deteriorated and the life is shortened. On the other hand, if the zinc concentration is reduced to prevent diffusion, the »working voltage increases and laser oscillation becomes difficult.

Further, in the conventional LD, the n-type cladding layer and the p-type cladding layer have a double hetero structure in which the A1 composition is larger than that of the active layer in order to confine the emitted light in the active layer. However, if the amount of A1 in the P-type cladding layer is increased to enhance light confinement, for example, the carrier concentration decreases, and as a result, the device resistance increases and the driving current increases. there were. On the other hand, if the amount of A 1 in the p-type cladding layer is reduced in order to lower the drive current, light confinement and carrier confinement are weakened, and the luminous efficiency is degraded.

Several semiconductor laser devices have been developed to solve the above problems. It is. For example, Japanese Unexamined Patent Application Publication No. 7-294784 discloses a semiconductor laser having a highly doped P-type second cladding layer (ridge: current confinement portion) in order to reduce device resistance. Has been described. However, during epitaxial growth, p-type dopants such as zinc diffuse into the active layer during the current application, resulting in a deterioration in device characteristics and a decrease in reliability. On the other hand, Japanese Patent Application Laid-Open No. 11-260880 discloses that a p-type second cladding layer (ridge: current constriction portion) and a p-type second cladding layer are used to prevent diffusion of a p-type dopant into an active layer. A semiconductor laser device provided with a carrier diffusion suppressing layer between the layers is described. However, the carrier diffusion suppression layer described here cannot sufficiently cope with changes in the diffusion state of the p-type dopant due to growth temperature, crystallinity, etc., and further has variations in element characteristics, which causes a problem in reproducibility of reliability. there were. Furthermore, Japanese Patent Application Laid-Open No. 11-878332 discloses that a p-type cladding layer and an active layer are provided between a p-type cladding layer and an active layer in order to prevent diffusion of a p-type dopant into the active layer. A semiconductor laser having a layer with a pan gap between the layer and the layer is described. However, this semiconductor laser has drawbacks in that the etching process of the ridge portion is complicated, and it is difficult to form a stable ridge shape, for example, a depression is formed on the upper side surface of the ridge portion by etching. Was. .

On the other hand, conventional LDs usually control the fundamental transverse mode by forming stripe-shaped ridges in the [111] direction (Fujii et al., Electronics Letters Vol. 23, Vol. 1). No. 8, 938-9339). By selecting the ridge stripe direction in the [111] direction, the luminous efficiency of the active layer composed of A1GaInP ordered crystal is improved compared to the [110] direction, and the threshold voltage is increased. This is because the current density can be reduced. However, in order to perform the fundamental transverse mode with higher output, it is necessary to make the ridge width narrower and the ridge height higher. In the [1-1-10] direction, large Joule heat is generated in the ridge. There was a problem that occurred.

In order to solve the above-mentioned problem in the ridge forming direction, a semiconductor laser having a stripe-shaped ridge formed in the [110] direction has been developed (Japanese Patent Application Laid-Open No. 7-193313). However, the ridge structure described here has an inverted mesa shape. In order to form this inverted mesa-shaped p-type third cladding layer, it is necessary to perform high-temperature growth (700 to 850 ° C) in a disordered state. It is not preferable to grow at a high temperature in order to form a disordered state, because the p-type dopant diffuses into the active layer during the growth process, the crystallinity of the active layer deteriorates, the life is shortened, and the reliability is reduced.

It is desired to provide a semiconductor light emitting device which solves the above-mentioned problems of the prior art and has low element resistance, thermal resistance, passing resistance and operating current, and is capable of high output operation and self-excited oscillation. Force No such semiconductor light emitting device has been provided so far. Disclosure of the invention

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the related art, and an object of the present invention is to provide a low output element, a low thermal resistance, a low through current, and a high operating current. It is to provide a simple semiconductor light emitting device. Another object of the present invention is to provide a semiconductor laser device having these characteristics and capable of self-sustained pulsation.

The present inventor has conducted intensive studies on the structure of a semiconductor device having a ridge structure in order to solve the above-described problems of the related art, and as a result, by configuring the ridge structure so as to satisfy a specific condition, the operation is improved. The inventors have found that a semiconductor light emitting device which can greatly reduce the current, can operate at high temperature, and can operate at high power can be obtained, and have completed the present invention.

That is, the object of the present invention is achieved by a semiconductor light emitting device having the following configuration.

[1] A substrate, a first conductivity type quad layer formed of at least one layer formed on the substrate, an active layer formed on the first conductivity type clad layer, and a substrate formed on the active layer. A first cladding layer of the second conductivity type, a second cladding layer of the second conductivity type having a stripe-shaped ridge structure formed on the first cladding layer of the second conductivity type, and a second cladding layer of the second conductivity type. First cladding of the second conductivity type so as to sandwich both sides of the ridge of the cladding layer. At least a current blocking layer formed on the first conductive layer and a second conductive type third cladding layer formed on the ridge of the second conductive type second cladding layer and on the current blocking layer near the ridge. A semiconductor light emitting device having a trapezoidal configuration, wherein a cross section orthogonal to a stripe longitudinal direction of the ridge structure satisfies the following expression.

0.05 <h / [(a + b) / 2] ku 0.5

(In the above formula, h is the height of the cross section, a is the upper bottom of the cross section, and b is the lower bottom of the cross section.)

[2] The semiconductor light emitting device according to [1], wherein the cross-section is a trapezoid whose lower bottom is longer than the upper bottom.

[3] The semiconductor light emitting device according to [1] or [2], wherein the cross section is a trapezoid having an upper base of 0.4 / xm to 4 μΐη.

[4] The semiconductor light emitting device according to any one of [1] to [3], wherein the cross section is a trapezoid having a height of 0.2 μΐη to 1.5 μπι.

[5] The semiconductor light-emitting device according to any one of [1] to [4], wherein the cross-sectional shape is asymmetrical.

[6] A substrate, a first-conductivity-type cladding layer formed on the substrate, comprising at least one layer, an active layer formed on the first-conductivity-type cladding layer, and formed on the active layer. A second conductive type first clad layer, a second conductive type second clad layer having a stripe-shaped ridge structure formed on the second conductive type first clad layer, and a second conductive type second clad layer. A current blocking layer formed on the second conductive type first cladding layer so as to sandwich both side surfaces of the ridge of the second cladding layer; and a current blocking layer formed on and near the ridge of the second conductive type second cladding layer. A second conductive type third cladding layer formed on the current blocking layer, and having a maximum light output of 8 OmW or more in single transverse mode oscillation in pulse driving at 25 ° C. Light emitting device.

[7] The semiconductor light emitting device according to [6], wherein the maximum light output is 20 OmW or more.

[8] The semiconductor light emitting device according to [6] or [7], wherein the light output density is 4 mW /// m ² or more. · [9] The semiconductor light emitting device according to any one of [1] to [5], wherein the semiconductor light emitting device is a self-pulsation type semiconductor laser device.

[10] A substrate, a first conductivity type clad layer comprising at least one layer formed on the substrate, an active layer formed on the first conductivity type clad layer, and A second conductive type first clad layer formed on the second conductive type first clad layer, a second conductive type second clad layer having a stripe-shaped ridge structure formed on the second conductive type first clad layer, and the second conductive type second clad layer. A current blocking layer formed on the second conductive type first cladding layer so as to sandwich both sides of the ridge of the second conductive type cladding layer; and on a ridge of the second conductive type second cladding layer. And a third cladding layer of the second conductivity type formed on the current blocking layer in the vicinity of the ridge, and has a maximum light output of 5 mW or more in single transverse mode oscillation in DC driving at 25 ° C. A semiconductor light emitting device, which is a self-pulsation type semiconductor laser device.

[11] The semiconductor light emitting device according to [10], wherein the light output density is not less than 0. SmW / ^ m ² .

[12] A substrate, a first-conductivity-type clad layer formed of at least one layer formed on the substrate, an active layer formed on the first-conductivity-type clad layer, and A second conductive type first clad layer formed, a second conductive type second clad layer having a stripe-shaped ridge structure formed on the second conductive type first clad layer, and a second conductive type second clad layer; A current blocking layer formed on the first cladding layer of the second conductivity type so as to sandwich both sides of the ridge of the second cladding layer; and a ridge on the second cladding layer of the second conductivity type. A second conduction type third cladding layer formed on the current blocking layer in the vicinity of the ridge, and self-excited oscillation type semiconductor laser which self-oscillates with an output of 5 mW or more at 70 ° C by DC driving. The device is a semiconductor light emitting device.

[1 3] The semiconductor light emitting device according to [1 2], which self-oscillates at an output of 5 mW or more at 75 ° C.

[14] The semiconductor light emitting device according to [12], which self-oscillates at an output of 1 OrnW or more at 70 ° C. [15] The semiconductor light emitting device according to [12], which self-oscillates at an output of 1 OmW or more at 75 ° C.

[16] The semiconductor light emitting device according to [12], wherein an oscillation threshold current at 25 ° C. by DC driving is 45 mA or less.

[17] The thickness of the current blocking layer is smaller than that of the second cladding layer of the second conductivity type.

The semiconductor light emitting device according to any one of [1] to [16].

[18] The semiconductor light emitting device according to any one of [1] to [17], wherein a refractive index of the current blocking layer is smaller than a refractive index of the second conductive type second cladding layer.

[19] The current blocking layer is made of a kind selected from the group consisting of A1GaInP, A1InP, A1GaAs and A1GaAsP. [1] to [18] The semiconductor light emitting device according to any one of claims 1 to 7.

[20] The current blocking layer is composed of A 1 G a As or A 1 G a As P

The semiconductor light emitting device according to [19].

[21] The semiconductor light emitting device according to any one of [1] to [20], further comprising an acid suppression layer on the ridge structure.

[22] The semiconductor light emitting device according to [21], wherein the oxidation suppressing layer is made of a material having a band gap larger than that of the material of the active layer.

[23] The semiconductor light emitting device according to [21] or [22], wherein both the second conductivity type second cladding layer and the oxidation suppressing layer are made of A1GaInP.

[24] The semiconductor light emitting device according to any one of [1] to [23], wherein a refractive index of the second conductive type third cladding layer is smaller than a refractive index of the second conductive type second cladding layer.

[25] The semiconductor light emitting device according to any one of [1] to [24], wherein constituent elements of the second conductive type third cladding layer are different from constituent elements of the second conductive type second cladding layer. .

[26] The semiconductor light emitting device according to any one of [1] to [25], wherein the resistivity of the second conductive type third cladding layer is lower than the resistivity of the second conductive type second cladding layer.

[27] The third cladding layer of the second conductivity type is made of AlGaAs or AlGaAsP. The semiconductor light emitting device according to any one of [1] to [26], which is configured.

[28] The semiconductor light emitting device according to any one of [1] to [27], further comprising a surface protection layer on the current blocking layer.

[29] The semiconductor light emitting device according to [28], wherein the surface protective layer is made of a material having a larger band gap than the material of the active layer. ■

[30] The semiconductor according to any one of [1] to [29], wherein the active layer contains at least Ga and In as constituent elements, or contains at least A1 and In. Light emitting device.

[31] The semiconductor light emitting device according to any one of [1] to [30], wherein the active layer includes a saturable absorber having a volume necessary for self-pulsation.

[32] The semiconductor light emitting device according to any one of [1] to [31], wherein the substrate has an off angle from a plane equivalent to the (100) plane.

[33] The semiconductor light-emitting device according to [32], wherein an off-angle direction of the substrate is within ± 30 ° from a direction perpendicular to a stripe longitudinal direction of the stripe-shaped ridge structure.

[34] The semiconductor light emitting device according to any one of [1] to [33], wherein the resonator length is 150 iim to 450 m. '

[35] The semiconductor light emitting device according to any one of [1] to [34], wherein the semiconductor light emitting device is a semiconductor laser.

[36] A substrate, a first-conductivity-type clad layer comprising at least one layer formed on the substrate, an active layer formed on the first-conductivity-type clad layer, and formed on the active layer A second conductive type second clad layer formed on the second conductive type first clad layer, and a second conductive type second clad layer formed on the second conductive type first clad layer. Forming a striped protective film on the second conductive type second clad layer, and partially etching the second conductive type second clad layer to form the second conductive type second clad layer in a striped shape. The current blocking layer is formed so as to sandwich both sides of the ridge of the second conductive type second clad layer, and the protective layer is removed. Forming a second cladding layer of the second conductivity type on the ridge of the second cladding layer of the second conductivity type and on the current blocking layer near the ridge, [1] to [35] ] The manufacturing method of the semiconductor light emitting device according to any one of the above.

[37] The method for manufacturing a semiconductor light emitting device according to [36], further comprising: after forming the current blocking layer, forming a surface protective layer on the current blocking layer.

In the semiconductor light emitting device of the present invention, a current blocking layer having a real guide structure is formed on both sides of a second conductive second cladding layer having a ridge structure whose cross-sectional structure is designed to satisfy a specific condition, Further, a second conductive third clad layer for confining light is provided on the ridge structure. With this configuration, according to the present invention, it is possible to provide a semiconductor optical device having a low element resistance, a low pass resistance and a low thermal resistance and capable of high-output operation. Brief Description of Drawings

FIG. 1 is a schematic sectional view of a semiconductor light emitting device having a configuration from the substrate of the present invention to the second conductive type third clad layer.

FIG. 2 is a schematic sectional view of a semiconductor laser according to a preferred embodiment of the present invention. FIG. 3 is a schematic explanatory view for explaining a state in a manufacturing process of the semiconductor laser used in the preferred embodiment of the present invention.

FIG. 4 is a schematic explanatory view for explaining a state in a manufacturing process of the semiconductor laser used in Examples 3 to 6 of the present invention.

FIG. 5 is a graph showing the relationship between the operating current and the optical output of the semiconductor laser manufactured according to the preferred embodiment of the present invention.

FIG. 6 is a graph showing the oscillation spectrum (a) and the visibility (b) of the semiconductor laser manufactured in Example 3 of the present invention. -FIG. 7 is a schematic explanatory view of a semiconductor laser using a conventional A1GaInP-based semiconductor material.

FIG. 8 is a schematic explanatory view of a conventional semiconductor laser using an A1GaInP-based semiconductor material. FIG. 9 is a schematic explanatory view of a conventional semiconductor laser using an A1GaInP-based semiconductor material.

FIG. 10 is a schematic explanatory view of a conventional semiconductor laser using an A1GaInP-based semiconductor material.

FIG. 11 is a graph showing current-light output characteristics of a semiconductor laser using a conventional A 1 G a In P semiconductor material.

FIG. 12 is a schematic explanatory view of a semiconductor laser using a conventional A1GaInP-based semiconductor material.

FIG. 13 is a graph showing the oscillation spectrum (a) and the visibility (b) of the semiconductor laser manufactured in Example 5 of the present invention.

FIG. 14 is a diagram showing a state of achievement of self-sustained pulsation of each semiconductor laser manufactured in Example 6 of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

The semiconductor light emitting device of the present invention will be specifically described with reference to the drawings.

In this specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit and an upper limit.

FIG. 1 is a schematic cross-sectional view of a semiconductor light emitting device having a configuration from the substrate of the present invention to the second conductive type third clad layer. As shown in FIG. 1, the semiconductor light emitting device of the present invention comprises a substrate 101, a first conductive type clad layer 102, and an active layer 106 formed on the first conductive type clad layer 102. A second conductive type first clad layer 107 formed on the active layer 106 and a second conductive type first clad layer 107 formed on the second conductive type first clad layer 107 having a stripe-shaped lid structure. A conductive type second cladding layer 108, a current blocking layer 109 formed on the second conductive type first cladding layer 107 so as to sandwich both sides of the ridge structure, and a second conductive type second cladding layer 108. And at least the second conductivity type third cladding layer 110 formed on the two current blocking layers 109 on the two cladding layers 108.

FIG. 2 is a schematic sectional view of a semiconductor laser according to a preferred embodiment of the present invention. Figure 2 The semiconductor laser according to the embodiment shown in FIG. 1 includes a substrate 201, a buffer layer 202 formed on the substrate 201, and a first conductivity type first cladding layer 203 formed on the buffer layer. A first conductive type second clad layer 204 formed on the first conductive type first clad layer 203, and an active layer 20 formed on the first conductive type second clad layer 204. 5, a second conductivity type first cladding layer 206 formed on the active layer 205, and an etching stop layer 207 formed on the second conductivity type first cladding layer. A second conductive type second cladding layer 208 having a ridge structure on the stripe formed on the etching stop layer 207, and a second conductive type second cladding layer 208 having a ridge structure on the etching stop layer 207. 2 A current blocking layer 209 formed so as to sandwich both sides of the cladding layer and a second conductive type second cladding layer 208 formed on the ridge structure. Oxidation suppression layer 210, surface protection layer (cap layer) 211 formed on current blocking layer 209, and second conductivity type third clad formed on surface protection layer 211 A layer 2 12, a contact layer 2 13 formed on the second conductive type third cladding layer 2 12, and a p-side electrode 2 formed on the contact layer 2 13 side and the substrate 201 side, respectively. 14 and n-side electrode 2 15.

In this specification, the expression “the B layer formed on the A layer” means that the B layer is formed such that the bottom surface of the B layer is in contact with the upper surface of the A layer, and that one or more layers are formed on the upper surface of the A layer. This includes both the case where the layer is formed and the layer B is formed on the layer. The above expression also includes the case where the upper surface of the A layer and the bottom surface of the B layer are partially in contact with each other, and in other portions, one or more layers exist between the A layer and the B layer. Specific aspects are apparent from the following description of each layer and specific examples of the examples.

In FIGS. 1 and 2, the conductivity and material of the substrates 101 and 201 are not particularly limited as long as a crystal having a double hetero structure can be grown thereon. Preferably, it is a semiconductor substrate having conductivity. Specifically, G a A s, I n P, G a P, Z n S e, Z n O, S i, A 1 2 0 3 or the like crystal substrate suitable for crystal thin film growth on the substrate, In particular, it is preferable to use a crystal substrate having a zinc blende structure. In that case, the substrate crystal growth surface is preferably a low-order surface or a surface crystallographically equivalent to it. In particular, the (100) plane is most preferred.

In this specification, the (100) plane does not necessarily have to be strictly a (100) plane, but includes a plane equivalent to the (100) plane, that is, a plane having an off-angle of about 30 ° at the maximum. I do. The upper limit of the off-angle is preferably 30 ° or less, more preferably 14 ° or less. The lower limit of the off angle is preferably at least 0.5 °, more preferably at least 2 °, further preferably at least 6 °, most preferably at least 10 °.

The direction of the off-angle of the substrates 101 and 201 is within ± 30 ° from the direction perpendicular to the direction in which the stripes constituting the ridge structure of the second conductive type second cladding layers 108 and 208 described later extend. Preferably, directions within 7 ° of soil are more preferred, and directions within ± 2 ° are most preferred. When the plane orientation of the substrates 101 and 201 is (100), the stripe direction of the ridge structure is preferably [0-11] or a direction equivalent thereto, and the off-angle direction is the [011] direction or the like. The direction is preferably within ± 30 °, more preferably within 7 °, and most preferably within ± 2 ° from the costly direction.

In this specification, the [01-1] direction refers to a general III-V or II-VI semiconductor that exists between the (100) plane and the [01-1] plane. · Define the [0 1-1] direction so that the [1-1] plane is the plane where the group V or group VI element appears, respectively.

The substrate 101, 201 may be a substrate of hexagonal type, for example, may be used a substrate made of _{_{A 1 2 0 3, 6 H}} -S i C , and the like.

As shown in FIG. 2, it is preferable to form a buffer layer 202 having a thickness of about 0.2 to 2 / zm on the substrate 201 so that defects of the substrate are not usually introduced into the epitaxial layer. In many cases, the same material as the substrate is used for the material of the buffer layer, for example, the first conductivity type of GaAs, GaP, InP, GaN, GaN, GInP, GInAs , G a InN, ZnS e, ZnSS e, ZnO, etc. are preferred. Good.

On the substrates 101 and 201, a compound semiconductor layer including the active layers 106 and 205 is formed. The compound semiconductor layer includes layers above and below the active layers 106 and 205 that have a lower refractive index than the active layer, of which the layer on the substrate side is the first conductivity type cladding layer (preferably the n-type cladding layer), The layers on the epitaxial side each function as a second conductivity type cladding layer (preferably a p-type cladding layer). The magnitude relationship between the refractive indices can be adjusted by appropriately selecting the material composition of each layer according to a method known to those skilled in the art. Active layer Contact Yopi cladding layers, for example, _{_{A 1 x Ga x As, (}} A 1 X G a χ _ χ) y I n! _ Y P, to changing the A 1 composition such as A 1 _X G a Thus, the refractive index can be adjusted.

As shown in FIG. 1, when the first conductivity type clad layer is a single layer, the first conductivity type clad layer 102 can be formed of a material having a lower refractive index than the active layer 106. In addition, the refractive index of the first conductivity type cladding layer 102 must be larger than the refractive index of the second conductivity type first cladding layer, the second conductivity type second cladding layer, and the second conductivity type third cladding layer, which will be described later. Is preferred. The first conductivity type cladding layer 102 is made of, for example, AlGaInP, A1InP, AlGaAs, AlGaAsP, A1GaInAs, GaInAsP, A It can be formed using a general III-V group or II-VI group semiconductor material such as 1GaInN, BeMgZnSe, MgZnSSe, and CdZnSeTe.

Carrier concentration of the first conductivity type cladding layer 102 is preferably lower limit is 1 X 10 ¹⁶ cm one ³ or more, more preferably 5 X 10 ¹⁶ cm one ³ or more, IX 10 ¹⁷ cm- ³ or more Is most preferred. On the other hand, it is preferable that the upper limit of the carrier concentration is 5 X 10 ¹⁹ cm one ³ or less, 5 XI 0 ¹⁸ more preferably cm at one ³ or less, and most preferably 2X 10 ¹⁸ cm one ³ below.

When the first conductivity type cladding layer 102 is formed of a single layer, the thickness is preferably about 0.5 to 4 jum, and more preferably about 1 to 3.

For example, as shown in the preferred embodiment of FIG. It may be composed of a plurality of layers having different concentrations and compositions. When the first conductivity type cladding layer is formed of a plurality of layers having different carrier concentrations, the carrier concentration of the first conductivity type second cladding layer 204 on the active layer 205 side is the first conductivity type second cladding layer on the substrate 201 side. 1 It is preferable that the carrier concentration is lower than that of the cladding layer 203. Kiyaria concentration of the first conductivity type first cladding layer 203 of the substrate 201 side, that the range of ^{^{1 X 10 16 ~3 X 10 18}} cm- 3 is ^{^{preferably, 5 X 10 16 ~2X 10 18}} c m_ 3 I like it. It is preferable that the thickness of the first conductive type second cladding layer 204 on the active layer 205 side be smaller than the thickness of the first conductive type first cladding layer 203. The lower limit of the thickness of the first conductivity type second cladding layer 204 is preferably 0.01 m or more, more preferably 0.03.μΐη or more, and the upper limit is preferably 1 m or less. More preferably, it is 0.7 μΐη or less. Examples of the case where the first conductivity type clad layer is formed of a plurality of layers having different compositions include, for example, a first conductive layer made of A1GaAs or A1GaAsP on the substrate 201 side. It is possible to exemplify an embodiment comprising a first cladding layer 203 of the first conductivity type and a second cladding layer 204 of the first conductivity type composed of A 1 Ga InP or A 1 InP which is closer to the active layer 205 than that layer. it can. The structure of the active layers 106 and 205 constituting the semiconductor light emitting device of the present invention is not particularly limited. In the example of FIG. 1, the active layer 106 has a multiple quantum well (MQW) structure. Specifically, the multiple quantum well structure includes an optical confinement layer (non-doped) 103, a quantum well layer (non-doped) 104, a barrier layer (non-doped) 105, a quantum well layer (non-doped) 104, and a confinement layer (non-doped) 103 Are sequentially stacked. The active layer has a multi-quantum structure having three or more quantum well layers, a barrier layer sandwiched between them, and an optical confinement layer stacked above the uppermost quantum well layer and below the lowermost quantum well layer. In addition to the well structure (MQW), for example, a single quantum well structure (SQW) comprising a quantum well layer and optical confinement layers sandwiching the quantum well layer from above and below, and a double quantum well structure (DQW) Is also good. By making the active layer a quantum well structure, it is possible to achieve a shorter wavelength (630 nm to 660 nm) and a lower threshold as compared with a single-layer Balta active layer. In the case of a self-pulsation type semiconductor laser, the number of wells can be made smaller than that of a normal non-self-pulsation single-mode laser in order to form a saturable absorber having a volume necessary for self-pulsation in the active layer. It is valid. Further, in this case, it is effective that compressive or tensile strain is applied to the quantum well layer in order to improve high-temperature operation. When the bow I strain is applied, oscillation is likely to occur in the TM mode, but the characteristics can be improved while the bandgap is kept large, which is effective for improving the performance of lasers in the short wavelength region.

Examples of the material of the active layers 106 and 205 in the semiconductor light emitting device of the present invention include GaInP, AlGaInP, GaInAs, AlGaInAs, GaInAsP, and A1GaInN. Examples can be given. In particular, in the case of a material containing Ga and In or A1 and In as constituent elements, a natural superlattice is easily formed, so that the effect of suppressing the natural superlattice by using an off-substrate increases.

The active layers at both ends of the optical waveguide preferably have a band gap that is transparent to light generated in the active layer in the current injection region at the center of the optical waveguide.

In order to realize a practical high-power laser, the lower limit of the total thickness of the active layer is preferably 2 nm or more, more preferably 25 nm or more, still more preferably 30 nm or more, and most preferably 35 nm or more. On the other hand, the upper limit of the total thickness of the active layer is preferably equal to or less than the thickness at which the quantum effect functions when the active layer has no strain. That is, the upper limit of the total thickness of the active layer is preferably 100 nm or less, more preferably 80 nm or less, and even more preferably 70 nm or less. When the active layer is strained, the thickness is preferably not more than the critical thickness. That is, the upper limit of the total thickness of the active layer is preferably 8 O nm or less, more preferably 60 nm or less, and even more preferably 5 O nm or less.

The preferred number of quantum wells is 1 to 5, preferably 1 to 4, more preferably 2 to 3, and most preferably 2 if the oscillation wavelength of a 600 nm red laser at room temperature (25 ° C) is 630 to 670 nm. The oscillation wavelength near room temperature is 670 ~ 700 η In the case of m, it is 1-5, preferably 1-4, more preferably 2-3, most preferably 2. The thickness of the quantum well is preferably 4, 3 to 7 nm, and more preferably 4 to 6 nm when the oscillation wavelength near room temperature (25 ° C.) is 630 to 670 nm. On the other hand, when the oscillation wavelength near room temperature (25 ° C.) is 670 to 700 nm, 6 to 10 nm is preferable, and 7 to 9 nm is more preferable.

In the case of a self-pulsation type semiconductor laser in which the active layer is formed of GaInP or A1GaInP, a single layer active layer may be used, but a shorter wavelength (630 nm to 665 (nm) In order to lower the threshold voltage, a multiple quantum well (MQW) structure composed of a quantum well layer and a barrier layer sandwiching the quantum well layer and / or a confinement layer is more preferable. Furthermore, in this case, in order to improve the high temperature operation, compressed into the quantum well layer _{_{(G a x I n _ X}} P, x! <0. 52) or pulling (Gax I i ^ - xP x > 0. 52) Is effective. If tensile strain is applied, oscillation in the TM mode becomes easier, but the characteristics can be improved while the band gap is increased. This is effective for improving the performance of lasers in the shorter wavelength range of 630 to 650 nm.

In order to form a saturable absorber having a volume required for self-sustained pulsation in the active layer, the total thickness of the active layer, that is, in the case of a multiple quantum well, the total thickness of each quantum well active layer is determined by the following equation. From the viewpoint of securing the volume of the supersaturated absorption region required for excitation oscillation, the lower limit is preferably 5 nm or more, more preferably 10 nm or more, still more preferably 15 nm or more, and most preferably 25 nm. From the viewpoint of suppressing COD at the end face, the upper limit is preferably 200 nm or less, more preferably 15 nm or less, still more preferably 100 nm or less, and most preferably 50 nm or less.

For the same reason, in order to realize a practical self-pulsation laser, the thickness of each layer of the active layer is, as a lower limit, preferably 2 nm or more, more preferably 3 nm or more, still more preferably 4 nm or more. Most preferably nm or more. From the viewpoint of suppressing COD on the end face, the upper limit is preferably 20 nm or less, more preferably 15 nra or less, still more preferably 9 nm or less, and most preferably 7 nm or less. It is preferable that the total thickness of the active layer (the sum of the thicknesses of all the quantum well layers in the active layer) should be at least a certain level for the ease of self-oscillation and the range in which self-oscillation can be sustained (temperature and optical output). . Specifically, the lower limit of the total thickness of the active layer is preferably 25 nm or more, more preferably 30 nm or more, and even more preferably 35 nm or more. On the other hand, the upper limit of the total thickness of the active layer is preferably equal to or less than the thickness at which the quantum effect functions when the active layer has no strain. That is, the upper limit of the total thickness of the active layer is preferably 100 nm or less, more preferably 80 nm or less, and even more preferably 70 nm or less. When the active layer is strained, the thickness is preferably not more than the critical thickness. That is, the upper limit of the total active layer thickness is preferably 80 nm or less, more preferably 60 nm or less, and even more preferably 50 nm or less.

The preferable number of quantum wells is 4 to 10, preferably 4 to 9, more preferably 7 to 9, when the oscillation wavelength of a 600 nm red laser at room temperature (25 ° C) is 630 to 67 Onm. Preferably, it is 7-8, most preferably 8, while when the oscillation wavelength near room temperature is 670-700 nm, it is 3-9, preferably 5-8, more preferably 6-8, and even more preferably 6-7, most preferably 7. When the oscillation wavelength near room temperature (25 ° C.) is 630 to 670 nm, the thickness of the quantum well is preferably 3 to 7 nm, more preferably 4 to 6 nm. On the other hand, when the oscillation wavelength near room temperature (25 ° C) is 670 to 700 nm, 6 to 1 O nm is preferable, and 7 to 9 nm is more preferable. -The optical confinement layer is effective from the viewpoints of increasing the confinement efficiency in the quantum well layer and preventing contamination (diffusion) of impurities such as Zn into the quantum well layer. By properly selecting the thickness of the confinement layer, it is possible to reduce the laser oscillation threshold current and improve the life. Specifically, from the viewpoint of securing the volume of the saturable absorption region required for self-pulsation, the thickness of the confinement layer is preferably 0.01 im or more, more preferably 0. μπι or more is more preferable, and 0.06 μπι or more is most preferable. From the viewpoint of suppressing COD at the end face, the upper limit is preferably 0.5 μηι or less, more preferably 0.3 or less, and even more preferably 0.15 μπι or less. And 0.1 μπι or less is most preferable.

When the oscillation wavelength of the 600 nm red laser at room temperature is 630 to 670 nm, the lower limit of the thickness of the light confinement layer is preferably 5 Onm or more, more preferably 6 Onm or more. The upper limit is preferably 20 Onm or less, more preferably 10 Onm or less. On the other hand, when the oscillation wavelength near room temperature is 670 to 700 nm, the lower limit is preferably 40 nm or more, more preferably 50 nm or more. The upper limit is preferably 150 nm or less, more preferably 100 nm or less. When the number of quantum wells is 6, 50 to 15 Onm is preferable, when the number of quantum wells is 7, 40 to 130 nm is preferable, and when the number of quantum wells is 8, 25 to 90 nm is preferable.

The carrier concentration in the active '1' active layer is not particularly limited, but the quantum well layer and the barrier layer are not undoped without any particular impurity doping. be 10 ¹⁷ cm one ³ or less) and have) reached the first or second conductivity type, and more preferred from the viewpoint of improving and stabilizing the performance of the device. in addition, at least close to the quantum well layer is also light confinement layer Preferably, the portion is undoped.

On the active layers 106 and 205, a second conductivity type cladding layer is formed. When an etching stop layer is formed, at least three cladding layers of the second conductivity type are formed. In the following description, the second conductive type first clad layers 107 and 206, the second conductive type second clad layers 108 and 208, and the second conductive type third clad layer 110 , 212 will be described as an example. When the etching stop layer is not formed, at least two second conductivity type cladding layers are formed.

The second conductivity type first cladding layers 107 and 206 can be made of a material having a lower refractive index than the active layers 106 and 205 in order to confine light in the active layer. For example, the second conductivity type first cladding layers 107 and 206 are formed of the second conductivity type A 1 Ga InP, A 1 InP, Al GaAs, Al GaAs P, Al Ga InAs, Ga InAs P, A 1 G a I nN,: one of B eMg ZnS e, MgZnSS e, CdZnS e Te, etc. General III-V and II-VI semiconductors can be used. When the first cladding layers 107 and 206 of the second conductivity type are made of a III-V compound semiconductor containing A1, substantially the entire surface on which they can be grown is GaAs, GaAsP, or GalnAs. It is preferable to cover with a group III-V compound semiconductor that does not contain A1, such as GaInP and GalInN, since surface oxidation can be prevented.

Kiyaria concentration of the second conductivity type first cladding layer 107, 206, the lower limit is preferably at 2X 10 ¹⁷ cm one ³ or more, it is laid more preferred is a 3X 10 ¹⁷ cm one ^3, 5X 10 ¹⁷ CM_ ³ Is most preferred. The upper limit of the Kiyaria concentration is preferably from 5 X 10 ¹⁸ cm- ^3, more preferably from 4X 10 ¹⁸ cm- ^3, and most preferably 2 X 10 ¹⁸ cm_ ^3.

If the thickness of the second conductive type first cladding layers 107 and 206 is too thin, the optical confinement becomes too strong and it becomes difficult to oscillate in a single transverse mode up to a high output. Leakage current of the blocking layers 109 and 209 is likely to occur. On the other hand, if the thickness is too large, the current spreads too much in the second conductive type first cladding layers 107 and 206 in the lateral direction, and the threshold current and operating current increase. In consideration of these, the lower limit of the thickness of the second conductive type first cladding layers 107 and 206 is preferably set to 0.03 πι or more, more preferably 0.05 μηι or more, and 0.07 μm or more. It is most preferable to set the above. The upper limit is preferably 0.5 or less, more preferably 0.3 / zm or less, and most preferably 0.2 μπι or less.

The refractive index of the second conductive type first cladding layers 107 and 206 may be smaller than the refractive index of the first conductive type cladding layer 102. In this way, it is possible to control the light distribution (near-field image) so that light can effectively seep from the active layer to the light guide layer side. In addition, since the optical waveguide loss from the active region (the portion where the active layer exists) to the zinc diffusion region can be reduced, laser characteristics and reliability in high-power operation can be improved.

As shown in FIG. 2, an etching process is performed on the second cladding layer 206 of the second conductivity type. Etching stop layer 207 can be formed for the purpose of preventing erosion of second conductive type first cladding layer 206 by the etching reagent at the time. The presence of the etching stop layer 207 makes it easy to prevent the formation of a high-resistance layer that increases the passage resistance at the regrowth interface at least when the second cladding layer 208 of the second conductivity type having the ridge structure is regrown. Will be able to

The material of the etching stop layer 207 is not particularly limited as long as it has resistance to the etching reagent during the etching process, that is, does not corrode. Further, the material of the etching stop layer 207 may have not only an erosion preventing function but also an oxidation preventing function. Specifically, A 1 _X G a _X A s (0≤χ≤1), 1 n _y G a! _ _Y P (0≤y≤ 1), (A 1 _U G a _a _ _u ) _v I n P (0 <≤ 1 0 <v≤ 1), I n p Al q Ga r n (0≤ρ≤1 0≤q≤l, 0≤ r≤ 1), I n iA 1 m Ga n As ( 0≤ 1≤ 1, 0≤m≤ 1, 0≤n≤l).

The thickness of the etching stop 207 is generally selected such that the band gap is larger than that of the material of the active layer 205, and the upper limit is preferably 20 nm 'or less, more preferably 10 nm or less, More preferably, it is 6 nm or less. The lower limit is preferably at least 1 nm, more preferably at least 1.5 nm, even more preferably at least 2 nm.

The conductivity type of the etching stop layer 207 is not particularly limited when it is removed by etching, but is preferably the second conductivity type. Further, it is preferable that the etching stop layer 207 is lattice-matched to the substrate 201 as much as possible. Further, from the viewpoint of reducing the operating current, it is preferable that the light from the active layer 205 is not absorbed by appropriately selecting the material and the thickness. .

On the second conductivity type first cladding layer 107 or the etching stop layer 207, a semiconductor layer having a stripe-shaped ridge structure is formed. The semiconductor layer having the ridge structure includes at least the second conductive type second cladding layers 108 and 208, and may include other semiconductor layers such as the oxidation suppression layer 210. The second conductive type third cladding layers 110 and 212 for confining light are provided on the bridge. The thickness of the second conductive type second cladding layer 108, 208 and the thickness of the second conductive type third cladding layer 110, 212 are determined so that the desired cladding layer thickness can be realized. By doing so, the thickness of the second conductive type second cladding layers 108 and 208 can be reduced, that is, the height of the ridge can be reduced. As a result, the passage resistance can be reduced, the influence of ridge asymmetry can be reduced, and a high kink level can be achieved.

The height of the ridge (the thickness of the second conductive type second cladding layers 108 and 208) is preferably low from the viewpoint of reducing the passage resistance as much as possible, but if the ridge height becomes too low. When the current blocking layers 109 and 209 are formed, overgrowth on the selective growth mask is likely to occur. When A1 is contained in the ridge portion, particularly in the second conductivity type second cladding layers 108 and 208, the resistivity tends to increase, and when A1 and In are contained, the resistivity further increases. This increase in resistivity is more pronounced for p-type. When the ridge cross section orthogonal to the longitudinal direction of the ridge has a forward mesa shape, the passage resistance is more likely to increase than in the case of an inverted mesa shape.

In the semiconductor light emitting device of the present invention, the ridge has a trapezoidal cross section satisfying the following expression.

0.05 <h / [(a + b). / 2] <0.5

In the above equation, h is the height of the cross section, a is the upper bottom of the cross section, and b is the lower bottom of the cross section. The range of h / [(a + b) / 2] is preferably from 0.07 to 0.45, more preferably from 0.1 to 0.35, and from 0.12 to 0. More preferably, it is from 3 to 15, most preferably from 0.15 to 0.25.

When a forward mesa direction must be formed, as in the case of A1GaInP, if the ridge is formed by etching, the sum of the two base angles of the trapezoid of the ridge cross section usually becomes smaller. (Specifically, 130 ° or less), the passage resistance tends to increase. From these viewpoints, the upper limit of the height of the ridge (height of the cross section) is preferably 1.5 / zm or less, more preferably 1.0 μπα or less, and 0.8 or less. More preferably, it is most preferably 0.55 jm or less. That's right. Further, the lower limit of the height of the ridge is preferably 0.1 m or more, more preferably 0.2 μπι or more, still more preferably 0.3 μηι or more, and 0.35 μηι or more. It is most preferred that the value is not less than ιη. By setting the height of the ridge within the above range, the total of both base angles of the trapezoid can be adjusted to a range of 130 to 140 °, preferably 135 to 140 °.

When oscillating in the single transverse mode, the upper limit of the width of the ridge bottom (the length of the bottom of the trapezoid) of the second conductivity type second cladding layer 108, 208 should be 5.0 m or less. Is preferably 4.0 μπι or less, more preferably 3.5 μπι or less, and most preferably 3.0 μηι or less. Further, the lower limit of the width of the bottom of the lid is preferably 0.5 μπι or more, more preferably 1.3 μπι or more, still more preferably 1.3 μπι or more, and 1.5 tm. It is most preferred that this is the case. When the current blocking layers 109 and 209 have a lower refractive index than the second conductive type second cladding layers 108 and 208, that is, in the case of a real refractive index waveguide structure (real guide structure), the current blocking layers 109 and 209 It is necessary to make the width of the bottom of the bridge narrower than in the case of the structure that absorbs the light generated by the active layers 106 and 205 (loss guide structure). This leads to a significant increase in passage resistance. From such a viewpoint, in the case of the real refractive index waveguide structure, the upper limit of the width of the ridge bottom is preferably 4.0 m or less, more preferably 3.5 μπι or less, and 3.0 μΐη or less. More preferably, it is most preferably 2.8 or less. Further, the lower limit of the width of the ridge bottom is preferably 0.5 / zm or more, more preferably 1.3 μπι or more, still more preferably 1.3 jum or more, and 1.5 jm or more. Is most preferred. If the width of the ridge bottom is Wa and the width of the ridge top is Wb, the upper limit of the average value (Wa + Wb) 2 in the actual refractive index waveguide structure is preferably 4.5 μπι or less, and 4 μπι. The following is more preferable, and 3.5 m or less is further preferable. The lower limit is preferably 1.8 μπι or more, more preferably 2 μπι or more, and even more preferably 2.2 μm or more. When the substrates 101 and 201 have an off-angle and stripes are formed in a direction perpendicular to the off-angle direction of the brackets, the cross-sectional shape of the ridge structure is generally left-right asymmetric. Then, the second conductive type third cladding layers 110 and 212 as light confinement layers are separately formed on the ridges (second conductive type second cladding layers 108 and 208), thereby reducing the ridge height. can do. As a result, even when the semiconductor light emitting device of the present invention has an off-angle, the influence of the ridge asymmetry can be reduced, and as a result, a high Kinkle level can be achieved.

When the ridge shape is asymmetric, the lower limit of I (one base angle) -one (the other base angle) I, which is the absolute value of the difference between one base angle and the other base angle, is preferably 2 ° or more. , 11 ° or more, and most preferably 15 ° or more. The upper limit is preferably 35 ° or less, more preferably 30 ° or less, and most preferably 25 ° or less.

For the same reason, when a wurtzite-type substrate is used, the direction in which the stripe region of the ridge structure extends is preferably, for example, [11-20] or [1-100] on the (0001) plane. For HVPE (Hydride Vapor Phase Epitaxy), either direction is acceptable, but for MOVPE, the [11-20] direction is more preferable. The material of the second conductive type second clad layers 108 and 208 is the same as that of the second conductive type first clad layers 107 and 206 described above, and is of the second conductive type A 1 G a InP, A 1 InP, A l General III-V, II-VI semiconductors such as GaAs, Al GaAs P, Al Ga InAs, Ga InAs P, A1GaInN, BeMg ZnS e, Mg ZnSS e, CdZnS eTe Can be used. However, from the viewpoint that the second conductive type second cladding layers 108 and 208 are transparent to light emitted from the active layers 106 and 205, the III-V group and the II-V group composed of at least three types of elements are used. -Preferably a group VI semiconductor, more preferably containing A1, more preferably containing A1 and In, most preferably A1GaInP or A1InP. Carrier concentration in the ridge (second conductive second cladding layer 108, 208) is preferably a lower limit is 1 X 10 ¹⁷ cm_ ³ or more, more preferably ³ X 10 ¹⁷ cm_ 3 or more, 5 X 10 Most preferably, it is ¹⁷ cm or more than ³ cm. The upper limit of the or carrier concentration is preferably 2 X 10 ¹⁹ cm one ³ or less, more preferably 5 X 1 0 ¹⁸ cm- ³ or less, that is 3 X 10 ¹⁸ cm one ³ or less Most preferred.

Both side surfaces of the ridge structure of the second conductive type second cladding layers 108 and 208 having a ridge structure are sandwiched between current blocking layers 109 and 209. At this time, the entire side surfaces of the ridge structure of the second conductivity type second cladding layers 108 and 208 may not be entirely sandwiched by the current blocking layers 109 and 209 from the upper end to the lower end. May be sandwiched between the current blocking layers 109 and 209. Since the current flows through the second conductive type second cladding layers 108 and 208 in a state where the current is confined by the current blocking layers 109 and 209, the passing resistance of the element is equal to the second conductive type second cladding layers 108 and 208. It largely depends on resistance. The effect of reducing the passing resistance of the present invention obtained by adjusting the thickness and the width of the second conductive type second cladding layers 108 and 109 having the ridge structure of the present invention is particularly the second conductive type second cladding layer. This is remarkable when the conductivity types of 108 and 208 are p-type. This is because the p-type has lower mobility and higher resistivity than the n-type, and the p-type is easier to diffuse dopant impurities (for example, zinc (Zn) and n-type Uses silicon (Si) as a dopant, but the p-type is easier to diffuse), and the p-type is more susceptible to the absorption of light emitted by the active layer. This is because increasing the carrier concentration of the second-conductivity-type second cladding layer and lowering the passing resistance as described above is not appropriate because it causes deterioration in the device characteristics and reliability of the laser.

Although not shown, an etching stop layer may be formed between the second conductive type second clad layers 108 and 208 and the second conductive type third clad layers 109 and 209. By forming the etching stop layer, the controllability of the ridge shape, particularly the width of the ridge bottom, of the second conductivity type second cladding layers 108 and 208 can be improved. The

Further, as shown in FIG. 2, an oxidation suppression layer 210 of the second conductivity type can be formed on the second cladding layer 208 of the second conductivity type. When the second conductivity type second cladding layer 208 is composed of a III-V compound semiconductor containing A1, the A1 composition of the oxidation suppressing layer 210 is the second conductivity type second cladding layer 2108. It is preferably smaller than the A1 composition of 08. By forming the oxidation suppressing layer 210 on the second conductive type second clad layer 208, the second conductive type third clad layer 212 can be re-grown at least on the ridge. The generation of a high-resistance layer that increases the passage resistance at the growth interface can be easily prevented. The material of the oxidation suppressing layer 210 is not particularly limited as long as it is hardly oxidized or a material that is easy to clean even if oxidized. As a specific example, an III-V compound semiconductor layer having a low content of an easily oxidizable element such as A1 can be given. When A1 is contained, the content of A1 is preferably 0.3 or less, more preferably 0.25 or less, and most preferably 0.15 or less. For example, AlGaInP or GaInP is preferred. Further, by selecting the material and thickness of the oxidation suppressing layer 210, it is preferable that the material be transparent to light generated in the active layer 205. In particular, in the case of a real refractive index guide, it is preferable to adopt such a form than in the case of a loss guide. The material of the oxidation suppression layer 210 is generally selected from materials having a larger band gap than the material of the active layer 205. However, even if the material of the band gap is smaller, the thickness of the oxidation suppression layer 210 is small. When the thickness is 30 nm or less, preferably 20 nm or less, and more preferably 10 nm or less, light absorption can be substantially negligible to some extent and thus can be used.

The current blocking layers 109 and 209 are formed on the second conductive type first clad layer 107 or the etching stop layer 2 7, and the second conductive type second clad layers 108 and 2. 08 are formed so as to sandwich both side surfaces. The current blocking layers 109 and 209 have a function of constricting the current so as to flow through the second conductive type second cladding layers 108 and 208. The material of the current blocking layers 109 and 209 may be a semiconductor or a dielectric. Semiconductors and dielectrics each have advantages and disadvantages as described below. Therefore, it is preferable to appropriately determine the material of the current blocking layer in consideration of these advantages and disadvantages.

When a semiconductor is used as the material of the current blocking layers 109 and 209, the heat conductivity is higher because of the higher thermal conductivity compared to the dielectric film, the cleavage is better, and the junction is down because it is easier to flatten. There are advantages such as easy assembly and easy formation of the contact layer over the entire surface, which makes it easy to lower the contact resistance. However, semiconductors have drawbacks such as the need to take measures such as surface oxidation when using high-A1 compounds such as A1GaAs and A1InP to reduce the refractive index. is there.

In the case of using a dielectric as the material of the current blocking layer 109, 209, for example, S i N _x, or the like can be used _{_{S i O 2, A 1 2}} 0 3, A 1 N. When a dielectric is used, a current blocking layer having a low refractive index and excellent insulating properties can be obtained. However, it has disadvantages such as poor heat dissipation due to low thermal conductivity, poor cleavage, and difficulty in assembling due to junction down due to difficulty in flattening.

Considering a lower refractive index than the second conductivity type second cladding layers 108 and 208, and lattice matching with the GaAs substrate, A 1 Ga As or AI GaAs P or A It is preferable to use lGaInP or A1InP. A1GaInP or A1InP has poorer thermal conductivity than A1GaAs or A1GaAsP, changes in refractive index due to formation of a natural superlattice, selective growth ( Since the In composition on the ridge side wall and bottom surface is unstable, if it is possible to prevent the deposition of poly on the protective film during selective growth (selective growth with the addition of HC1), A 10 & 8 3 or 8 1 It is more preferable to select GaAsP. However, in the case of Al GaAs or A 1 Ga As P, since A 1 As and A 1 P show deliquescence, the upper limit of the A 1 composition is preferably 0.97 or less, more preferably 0.95 or less. , 0.93 or less is most preferred. Since it is necessary to have a lower refractive index than the second conductivity type second cladding layers 108 and 208, the lower limit of the A1 composition is preferably 0.3 or more, more preferably 0.35 or more, and 0.4 or more. Most preferred.

The refractive index of the current blocking layers 109 and 209 is sandwiched between the current blocking layers 109 and 209. The refractive index of the second cladding layers 108 and 208 of the second conductivity type is made lower (real refractive index waveguide structure). By controlling such a refractive index, it becomes possible to reduce the operating current as compared with the conventional loss guide structure. The lower limit of the refractive index difference between the current blocking layers 109 and 209 and the second conductivity type second cladding layers 108 and 208 is 0.001 or more when the current blocking layers 109 and 209 are formed of a compound semiconductor. It is more preferably 0.003 or more, and most preferably 0.007 or more. The upper limit of the difference in the refractive index is preferably 1.0 or less, more preferably 0.5 or less, and most preferably 0.1 or less. When the current blocking layers 109 and 209 are made of a dielectric material, the lower limit is preferably 0.1 or more, more preferably 0.3 or more, and more preferably 0.7 or more. Is most preferred. Further, the upper limit of the refractive index difference is preferably 3.0 or less, more preferably 2.5 or less, and most preferably 1.8 or less.

The conductivity type of the current blocking layers 109 and 209 may be either the first conductivity type or a high resistance (undoped or doped with deep-forming impurities (0, Cr, Fe, etc.)), or a combination of the two. Or a plurality of layers having different conductivity types or different compositions. For example, a current blocking layer formed in the order of the second conductive type or high resistance semiconductor layer and the first conductive type semiconductor layer from the side close to the active layers 106 and 205 can be preferably used. From the viewpoint of the current blocking function, the conductivity type of the current blocking layers 109 and 209 is preferably the first conductivity type. When the current blocking layers 109 and 209 are of the first conductivity type, there is a problem that if the carrier concentration is too low, the current leaks, whereas if the carrier concentration is too high, the loss due to light absorption increases. The lower limit of the carrier concentration of the current blocking layer from these viewpoints is preferably at 1 X 10 ¹⁶ cm one ³ or more, more preferably 1 X 10 ¹⁷ cm one ³ or more, 3 X 10 ¹⁷ cm one ³ It is most preferred that this is the case. The upper limit of the Kiyari § concentration is preferably 2 X 10 ¹⁹ cm_ ³ or less, more preferably 5 X 10 ¹⁸ cm one ³ or less, and most not more 3 X 10 ¹⁸ cm one ³ or less preferable.

If the thickness of the current blocking layers 109 and 209 made of a semiconductor is too thin, there is a problem of current leakage. Problem. From such a viewpoint, the lower limit of the thickness of the current blocking layers 109 and 209 made of a semiconductor at the flat portion beside the ridge is preferably 0.03 / zm or more, more preferably 0.1 μπι or more, and 0.2 m or more. The above is the most preferable. Also, the upper limit of the thickness (d) of the current blocking layer at the flat portion beside the ridge is preferably h + 0.2 μπι or less, based on the height (h) of the ridge, and is preferably h or less. Is more preferable, and h−0.05 m or less is most preferable. When the thickness of the current blocking layer on both sides of the ridge is larger than the thickness of the flat portion, 0.8 d / h 2 is preferable, 0.9 d / h 1.5 is more preferable, 1 <d / h <1.3 is more preferable.

Note that, as described above, the material of the current blocking layers 109 and 209 is preferably formed of A 1 GaAs from the viewpoint of overgrowth in the selective growth protective film. That is, when the current blocking layers 109 and 209 are formed of A1GaInP or A1InP, the problem that overgrowth is likely to occur in the selective growth protective film and the composition differs between the ridge side and the flat portion There is a problem. On the other hand, when the current blocking layers 109 and 209 are formed of AlGaAs, overgrowth is relatively unlikely to occur, and the composition is uniform between the ridge and the flat portion. For this reason, the current blocking layers 109 and 209 are preferably formed of A1GaAs.

The current blocking layers 109 and 209 are two or more layers having different refractive indices, carrier concentrations or conductivity types for controlling light distribution (particularly lateral light distribution) and improving current blocking function. May be formed. -As shown in FIG. 2, a surface protection layer 211 may be formed on the current blocking layer 209. By forming the surface protective layer 211, surface oxidation of the current blocking layer 209 can be suppressed, and the current blocking layer is prevented from being damaged or etched when the selective growth protective film is removed. And increase during regrowth The surface of the current blocking layer can be prevented from being roughened at the temperature stage, and the surface morphology and the crystallinity of the regrown layer can be improved. When the current blocking layer 209 is transparent to the light generated in the active layer 205, the surface protection layer 211 is also transparent to the light generated in the active layer 205, that is, the surface protection layer 211 is more transparent than the material of the active layer 205. Preferably, the bandgap is formed of a large material. When the current blocking layer is made of a dielectric material and is particularly a real refractive index guide, it is preferable to adopt such a form as compared with a loss guide. However, even if the material has a small band gap, if the thickness is 3 Onm or less, preferably 20 nm or less, and more preferably 10 nm or less, light absorption can be practically neglected to some extent. It can be used as a material for the surface protective layer 211 in the invention. The A1 composition of the surface protective layer 211 is preferably smaller than the A1 composition of the current blocking layer 209. Various materials can be used as the material of the surface protective layer 211, but the surface morphology of the regrowth due to the surface roughness of the underlayer due to the substitution of the group V element at the temperature rise stage during the regrowth ゃ prevents a decrease in crystallinity Therefore, it is preferable that the material is the same as that of the upper surface of the lid, that is, the second conductive type second cladding layers 108 and 208 or the antioxidant layer 210, and in particular, it is A 1 Ga InP or Ga InP. Is preferred. Although the conductivity type of the surface protective layer 211 is not particularly limited, the current blocking function can be improved by using the second conductivity type.

Third conductive type third cladding layers 110 and 212 are formed on the ridges of the second conductive type second cladding layers 108 and 208 and on the current blocking layers 109 and 209 near the ridges. The third cladding layers 110 and 212 of the second conductivity type may cover all over the current blocking layers 109 and 209, or may cover only the vicinity of the ridge. The second conductive type third cladding layers 110 and 212 are formed of a material having a lower refractive index than the active layers 106 and 205. For example; second conductivity type Al Ga I nP, A 1 I nP, A 1 G a A s N Al GaAs P, Al Ga I nAs, G a I n A s P, Al Ga I nN, B eMgZnS e, General III-V and II-VI semiconductors such as MgZnSSe and CdZnSeTe can be used.

If the thickness of the second conductive type third cladding layer 110, 212 is too small, light confinement will occur. As a result, the light absorption becomes remarkable in the contact layer 213, and the threshold current and the operating current increase. On the other hand, if the thickness is too large, the passage resistance increases, and this increase in the passage resistance becomes a serious problem in a material having a high resistivity such as p-type AlGaInP. Therefore, it is preferable to use A 1 Ga As or A 1 Ga As P as the material of the third cladding layer of the second conductivity type, and to set the lower limit of the thickness of the third cladding layers 110 and 212 of the second conductivity type to 0. It is preferably at least 1 jum, more preferably at least 0, more preferably at least 0.8, most preferably at least 1.1 m. Further, the upper limit of the thickness of the second conductive type third cladding layers 110 and 212 is preferably 3 μπι or less, more preferably 2.5 m or less, and 2 μΐη or less. More preferably, it is most preferably 1.6 μπι or less. In the case of a self-pulsation type semiconductor laser, the lower limit of the thickness of the second conductive type third cladding layers 110 and 212 is preferably 0.1 zm or more, more preferably 0. It is more preferably at least 3 μπι, most preferably at least 0.4 μπι. The upper limit of the thickness of the second conductive type third cladding layers 110 and 212 is preferably 2 m or less, more preferably 1.5 m or less, and more preferably 1 m or less. More preferably, it is most preferably 0.8 μπι or less.

The lower limit of the carrier concentration of the second conductivity type third cladding layer 1 10, 212 is preferably at 1 X 10 ¹⁷ CMT ^"3 or more, more preferably 3 X 10 ¹⁷ cm one ³ or more, 5 X and most preferably 10 ¹⁷ CM_ is ³ or more. the upper limit of the carrier concentration is preferably 2 X 10 ¹⁹ cm- ³ or less, more preferably 5 X 10 ¹⁸ cm- ³ hereinafter, 3 most preferably X 10 ¹⁸ cm is one ^3. the refractive index of the second conductive type third clad layer 1 10, 212 is smaller than the refractive index of the second conductive type second clad layer 108, 208 Thereby, light leakage to the contact layer side of the second conductivity type can be reduced, the threshold current can be reduced, and the thickness of the third cladding layer of the second conductivity type can be reduced. The upper limit of the refractive index difference is preferably 0.1 or less. Ma It is more preferably 0.07 or less, and further preferably 0.05 or less. The lower limit of the difference in refractive index is preferably 0.001 or more, more preferably 0.002 or more, and even more preferably 0.003 or more. The material of the third cladding layers 110 and 212 of the second conductivity type is A 1 Ga As, A 1 Ga As P from the viewpoint of lowering the resistivity or thermal resistance than the second cladding layers 108 and 208 of the second conductivity type. From the viewpoint of further lowering the refractive index than the second conductivity type second cladding layers 108 and 208, the lower limit of the A1 composition is preferably 0.67 or more, more preferably 0.72 or more, and 0.76 or more. The above is most preferred. Since A1 As and A1 P exhibit deliquescence, the upper limit of the A1 composition is preferably 0.97 or less, more preferably 0.93 or less, and most preferably 0.79 or less. However, in the case of a self-pulsation type semiconductor laser, the value is most preferably 0.89 or less.

As shown in FIG. 2, on the third cladding layers 110 and 212 of the second conductivity type, in order to reduce the contact resistance with the electrode material, a (second conductivity type) contact having a low resistance (high carrier concentration) is used. Preferably, layer 213 is formed. In particular, it is preferable to form the electrode after forming the contact layer on the entire surface of the uppermost layer (the second conductive type third cladding layer 212) on which the electrode is to be formed. The material of the contact layer 213 is usually selected from a material having a band gap smaller than that of the cladding layer, and more preferably a material having a smaller band gap than that of the active layer. Specifically, GaAs, GaAsP, GaInAs, GaInP, GaIn It is preferable to use a group III-V compound semiconductor that does not contain A1, such as InN, because surface oxidation can be prevented.

In addition, the contact layer 213 preferably has a low resistance and an appropriate carrier density in order to obtain ohmicity with the metal electrode. The lower limit of the carrier density of the contact layer 213 is preferably at 1 X 10 ¹⁸ cm- ³ or more, more preferably 3X 10 ¹⁸ cm- ³ or more, and most not more 5X 10 ¹⁸ cm one ³ or more I like it. The upper limit of the Kiyaria concentration is preferably 2 X 10 ²⁰ cm one ³ or less, more preferably 5 X 10 ¹⁹ cm one ³ or less, most 3 X 10 ¹⁸ cm one ³ below der Rukoto preferable. The thickness of the contact layer 213 is from 0 to 丄. ^ !!! It is more preferably 0.2 to 7 m, and most preferably 1 to 5 μπι.

Further, an intermediate band gap layer of the second conductivity type may be formed between the second conductive third clad layer 212 and the contact layer 213. As a result, the passage resistance due to the hetero barrier between the third cladding layer 212 of the second conductivity type and the contact layer 213 can be reduced. The lower limit of Kiyaria density of the intermediate Bandogiyappu layer is preferably 1 X 1 0 ¹⁷ cm one ³ or more, Ri preferably good is at 5 X 10 ¹⁷ cm one ³ or more, 1 X 10 ¹⁸ cm one ³ or more Is most preferred. The upper limit of the carrier density of the intermediate bandgap is, 5 X 10 ¹⁹ It is rather preferable cm_ is ³ or less, more preferably 1 X 10 ¹⁹ cm one ³ or less, 5 X 10 ¹⁸ cm- ³ or less Is most preferred. Further, the thickness of the intermediate band gap layer is preferably 0.01 to 0.5 μπι, more preferably 0.02 to 0.3 μηα, and 0.03 to 0.2 m. Most preferably.

In the structure of the semiconductor light emitting device of the present invention, first, the thickness of the active layer and the composition of the cladding layer are determined to obtain a desired vertical divergence angle.

Generally, narrowing the vertical divergence angle promotes light seepage from the active layer to the cladding layer, lowering the light density at the end face, and improving the optical damage (COD) level at the output end face be able to. For this reason, when high output operation is required, the vertical divergence angle is set to be relatively narrow, but the lower limit of the vertical divergence angle is determined by the oscillation threshold current due to the reduction of optical confinement in the active layer. There is a limitation due to the suppression of deterioration of the temperature characteristics due to the overflow of the carrier, preferably 12 ° or more, more preferably 14 ° or more, and most preferably 15 ° or more. Is also preferred. The upper limit of the vertical divergence angle is preferably 30 ° or less, more preferably 25 ° or less, and most preferably 22 ° or less. In general, when the vertical divergence angle is increased, the saturable absorption region in the active layer is increased, and self-sustained pulsation is likely to occur. For this reason, in the case of a self-pulsation type semiconductor laser, the vertical spread angle is set relatively large. However, the vertical spread angle is large Too much combusting will reduce the optical damage (COD) level of the emission end face and the light receiving efficiency of the optical system detector. Conversely, if too small, the supersaturated absorption region will be small, and self-pulsation will occur. It becomes difficult. For this reason, the lower limit of the vertical divergence angle is preferably 24 ° or more, more preferably 27 ° or more, even more preferably 29 ° or more, and 32. The above is most preferred. On the other hand, the upper limit of the vertical spread angle is preferably 42 ° or less, more preferably 40 ° or less, even more preferably 38 ° or more, and most preferably 36 ° or less.

Next, when the vertical divergence angle is determined, the structural parameters that largely govern the high output characteristics of the semiconductor light emitting device of the present invention are the distance (dp) between the active layers 106 and 205 and the current blocking layers 109 and 209 and the ridge. It is the stripe width (Wb) at the bottom (hereinafter referred to as the “stripe width”). Normally, the second conductivity type first cladding layers 107 and 206 are present between the active layers 106 and 205 and the current blocking layers 109 and 209, in which case, dp is the second conductivity type first cladding layer. The thickness of layers 107 and 206 is obtained. When the active layers 106 and 205 have a quantum well structure, the distance between the active layer closest to the current blocking layer and the current blocking layer is dp.

When designing a self-pulsation type semiconductor laser, if the vertical spread angle is too narrow, the second conductivity type first cladding layer is too thin, or the stripe width is too wide, self-pulsation occurs. It may be gone. Conversely, if the vertical divergence angle is too large, the second conductivity type first cladding layer is too thick, or the stripe width is too narrow, the self-excited oscillation occurs, but the operating current becomes too large. Or deteriorate the laser characteristics. Also, in order to maintain self-sustained pulsation stably even at high temperatures, it is better to set dp as small as possible. The reason is that the smaller the dp, the smaller the lateral current leakage to both sides of the ridge, and the more it becomes possible to form a saturable absorption region in the active layer sufficient for self-pulsation even at high temperatures. It is. Therefore, in order to achieve self-sustained pulsation, it is necessary to control the above dp and W within an appropriate range with good controllability. That is, for dp, 0.003 to 0.5 m is preferable, and 0.04 to 0.25 / ^ m is more preferable. 0.05 to 0.19 μπι is more preferred, and 0.06 to 0.15 μπι is particularly preferred. As for W, 1-4 μηι is preferred, 1.2-3.5 / zm is more preferred, 1.6-2.9 jLtm is more preferred, and 1.9-2.5 / xm is particularly preferred. preferable. However, if the purpose of use (where to set the divergence angle, etc.) or the material system (refractive index, resistivity, etc.) is different, the optimum range will shift slightly. It should also be noted that this optimum range affects each of the above structural parameters.

Stripe width (width of aperture) W1 and thickness of cladding layer on both sides of ridge dp As a guideline for optical design to satisfy the self-sustained pulsation condition, the effective lateral refractive index step inside the active layer is 2 ~ 7 X 10_ ³ about, it is necessary to set the light oozing ratio Γ & c t. out of the ridge both sides to about 10 to about 40%.

Also, since the volume of the saturable absorber is determined by the cross-sectional X resonator length, the resonator length also needs to be optimized. The lower limit of the length of the resonator is preferably 150 μπι or more, more preferably 200 μπι or more, further preferably 250 μπι or more, and most preferably 270 m or more. The upper limit is preferably 600 m or less, more preferably 500 μπι or less, further preferably 450 μπι or less, and most preferably 370 μπι or less.

The method for manufacturing the semiconductor light emitting device of the present invention is not particularly limited. What is manufactured by any method is within the scope of the present invention as long as it satisfies the above requirements of the present invention.

In manufacturing the semiconductor light emitting device of the present invention, a conventionally used method can be appropriately selected and used. The method of growing the crystal is not particularly limited. For the crystal growth of the double hetero structure and the selective growth of the ridge portion, a metal organic chemical vapor deposition method (MOCVD method), a molecular beam epitaxy method (ΜΒΕ method), Known growth methods such as hydride or halide vapor phase epitaxy (VPE) and liquid phase epitaxy (LPE) can be appropriately selected and used.

As a method for manufacturing a semiconductor light emitting device of the present invention, first, a step of forming a first conductive type first clad layer on a substrate and a step of forming an active layer on the first conductive type clad layer Forming a second conductivity type first cladding layer on the active layer; and forming a second conductivity type second cladding layer having a stripe-shaped ridge structure on the second conductivity type first cladding layer. Forming a current blocking layer on both sides of the second conductive type second cladding layer on the second conductive type first cladding layer; and forming a current blocking layer on the second conductive type second cladding layer. The step of forming the second conductivity type third cladding layer on the ridge and at least on a part of the current blocking layer can be exemplified. In addition, a step of forming a buffer layer on the substrate, a step of forming an etching stop layer on the first cladding layer of the second conductivity type, and a step of forming an acid suppression layer on the second cladding layer of the second conductivity type And forming a surface protective layer on the current blocking layer, and forming a contact layer on the second conductive type third cladding layer.

The specific growth conditions of each layer vary depending on the composition of the layer, the growth method, the shape of the device, etc.When the III-V compound semiconductor layer is grown by MOCVD, the double heterostructure Temperature 650 to 750 ° C, VIII ratio about 20 to 60 (for A1GaAs) or about 300 to 600 (for InGaAsP, AlGaInP), growth temperature for NAM and block regions It is preferable to carry out at a temperature of 600 to 700 ° C., a V / III ratio of about 40 to 60 (for A 1 Ga As), or about 350 to 550 (for InGaAs P and Al Ga In P).

In particular, when the current blocking layer formed by selective growth using a protective film contains Al, such as A1GaAs and A1GaInP, a small amount of HC1 gas is introduced during growth to mask Very preferred, as it prevents the deposition of poly on top. If the composition of A1 is higher, or the mask width or mask area ratio is larger, and other growth conditions are constant, poly deposition is prevented and selective growth is performed only on the exposed surface of the semiconductor (selective Mode)), the amount of HC1 introduced required increases. On the other hand, if the introduction amount of HC 1 gas is too large, the growth of the A 1 Ga As layer does not occur, and the semiconductor layer is etched instead. (Etching mode) Force The other growth conditions become more constant as the A 1 composition increases. In this case, the amount of introduced HC 1 required to enter the etching mode increases. For this reason, the optimal amount of HC1 introduced is trimethylaluminum It greatly depends on the number of moles of group III raw material including A1 such as rubber. Specifically, the lower limit of the ratio of the number of moles of HC1 supplied and the number of moles of group III material containing A1 (HC1 / III group) is preferably 0.01 or more, more preferably 0.05 or more. Is more preferable, and most preferably 0.1 or more. The upper limit is preferably 50 or less, more preferably 10 or less, and most preferably 5 or less. On the other hand, when the compound semiconductor layer containing In is selectively grown (in particular, HC1 is introduced), it is easy to control the composition.

When performing ridge formation or selective growth, a protective film can be used. Preferably the protective film is a dielectric, specifically, S iN _x film, S i 0 ₂ film, S i ON film, A l 2_Rei_3 film, Zetaitaomikuron film, S i C film Contact Yopi amorphous S selected from the group consisting of i. The protective film is used when the ridge is formed by selective regrowth using MOCVD or the like as a mask.

When the semiconductor light emitting device of the present invention is used as a semiconductor laser, the semiconductor laser may be a light source for information processing (usually an A1GaAs system (wavelength around 780 nm), an A1GaInP system (wavelength 600 nm). nm band), InGaN system (wavelength around 400 nm)), signal light source for communication (usually using ItiGaAsP or InGaAs as active layer 1.3 μm band, 1.5 Light source for laser and fire excitation (InGaAs strain quantum well active layer Near 980 nm using ZGaAs substrate, InGaAsP strain well active layer Near 1480 nm using ZInP substrate) Examples include various devices that require particularly high-output operation, such as communication semiconductor laser devices such as lasers. When the semiconductor laser of the present invention is driven by a high-speed pulse, the output in the single transverse mode is preferably 8 OmW or more, more preferably 10 OmW or more, and more preferably 12 OmW or more. More preferably, it is particularly preferably 16 OmW or more. Further, the semiconductor laser of the present invention preferably has a low pass resistance when driven, preferably 8 Ω or less, more preferably 7 Ω or less, and more preferably 6 Ω or less. Most preferred.

In the case of a self-pulsation type semiconductor laser, when it is driven by DC at 25 ° C, The maximum light output in the single transverse mode is preferably 5 m or more, more preferably 7 mW or more, and even more preferably 1 OmW or more. Also, the optical power density is preferably at 4 mW / m ² or more, more preferably SMW / jum ² than on, still more preferably les it is 8 mWZiU m ² or more. Further, the self-pulsation type semiconductor laser preferably has a low passing resistance when driven, preferably 8 Ω or less, more preferably 7 Ω or less, and more preferably 6 Ω or less. Most preferably. A typical self-sustained pulsation semiconductor laser of the present invention oscillates at 75 ° C with an output of 5 mW or more. If a specific example is shown in relation to the temperature, a typical self-pulsation type semiconductor laser of the present invention oscillates with a power of 5 mW at 70 ° C. and 5 mW at 75 ° C. Self-oscillates at output, self-oscillates at 1 OmW output at 70 ° C, and self-oscillates at 1 OmW output at 75 ° C. Further, the oscillation threshold current at 25 ° C. in direct current (DC) driving is, for example, 45 mA or less, preferably 4 OmA or less, and more preferably 35 mA or less.

The semiconductor laser of the present invention is also effective as a communication laser in that a nearly circular laser increases the coupling efficiency with the fiber. A laser having a single far-field image can be used as a laser suitable for a wide range of uses such as information processing and optical communication. Further, the structure of the present invention can be applied to a light emitting diode (LED) of an edge emitting type or the like other than the semiconductor laser.

Hereinafter, the present invention will be described in more detail with reference to specific examples. Materials, reagents, ratios, operations, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of this effort is not limited to the following specific examples. -(Example 1)

In this example, the semiconductor light emitting device shown in FIG. 3 was manufactured. N-type G a A s (n = 1 X 10) with a thickness of 350 and off from (100) plane by 10 ° in [011] direction ¹⁸ cm- ³⁾ on the substrate 301 by MOCVD, n-type thickness _{2. Ομπι (A 1 0. 7 Ga} 0. 3) o. 5 I n 0. 5 P (n = 8 X 10 17 cm - ^3, refractive index 3.2454) clad layer 302, (.... a 1 o 5 G a 0 J 0 5 I n 0 5 P light confining layer (non-doped) 321, thickness 5 nm of G a. . _₅ I n .. ₅ P strained quantum well layer (undoped) 322, a thickness of _{_{5 nm (a 1 0. 5}} Ga 0. 5) 0. 5 I n 0. 5 P Paglia layer (non-doped) 323, thickness is 0 and ₀ of 511111. _₅ I n .. ₅ P strained quantum well layer (non-doped) 324, a thickness of 5 nm of _{_{(a 1. · 5 Ga 5)}} 0. 5 I η 0 · 5 P Roh Li a layer ( _{doped) 325, 0 a 0. 5 I} n 0 thick five hundred and eleven thousand one hundred eleven. ₅ P strained quantum well layer (undoped) 326及Pi _{_{(a 1 0. 5 Ga 0.}} 5) I n .. 5 P light confining layer ( doped) 327 sequentially stacked three comprising quantum well the (TQW) active layer 303, a thickness of 0. 15 p-type _{μπι (a 10. 7 G a 0.} 3) o.5 I n 0. 5 P ( p = l x 10 ¹⁸ cm— ³ , refractive index 3.2454) Type first cladding layer 304, a thickness of 5 nm p-type _{_{_{G a 0. 5 I n 0}}} . 5 P (p = 1 X 10 1 8 cm- 3) p -type etching stop layer 305 made of, thickness 0. . of _{5 μπι (. a 10. 7 Ga} 0 3) 0. 5 I n 0 5 P (Zn ^{-doped: p = l X 10 18 cm-} 3, the refractive index 3. 2 454) p-type second clad consisting of layer 306, a thickness of 0. O l / zm p-type _{_{_{(Al 0. 2 Ga 0.}}} 8) 0. 5 I n 0. 5 p -type oxidation control consisting of ^{P (p = l X 10 18} cm one ³⁾ A double hetero structure was formed by sequentially laminating layers 307. (Fig. 3 (a).) Next, a 100 nm-thick SiN _x protective film was formed on the surface of this double hetero substrate by plasma CVD. After depositing a number of layers, a large number of striped SiO _x protective films 351 were formed by photolithography using the [01-1] direction (the direction perpendicular to the off direction of the substrate) as a longitudinal direction (Fig. 3 (b )).

Next, the surface of the etching stop layer 305 was subjected to wet etching by using the striped SiN _x protective film 351 so that the stripe width at the bottom of the ridge was 2.5 μπι. At this time, the width of the upper part of the ridge is 1.7 μπι, and the ridge shape is asymmetric, and the sum of the two base angles is 105 ° (the base angle of one side is 62 ° and the base angle of the other is 43 °) Met. (Fig. 3 (c)). At this time, a hydrochloric acid-based mixed solution or a sulfuric acid-based mixed solution was used as an etching solution for wet etching. The portion removed by the etching for forming the ridge using the above-mentioned striped SiN _x protective film 351 is selectively grown using the MOC VD method to form an n-type A having a thickness of 0.4 μπι. 10. ₉ Ga 0.0s current blocking layer (n = 2 x 10 ¹⁸ cm- ³ , refractive index 3.1 1590) 308 and thickness 0.011! ! Type _{_{_{(A l 0. 7 Ga 0}}} . 3) 0. 5 I n 0. 5 P surface protective layer ^{(η = 1 X 10 18 cm-} 3) 309 was formed '(FIG. 3 (d)). After that, the striped SiN _x protective film 351 is removed by hot etching using a buffered hydrofluoric acid solution or dry etching using a gas such as SF ₆ or CF ₄ (FIG. 3 (e)). Pi MOCVD method by a thickness of 0. 8 m of the p-type _{_{_{a l 0. 78 Ga 0.}}} 22 As third cladding layer ^{(p = 1 X 10 18 cm-} 3, the refractive index 3.2407) 310, thickness 0. p-type a 1 ₀ of _0. ₃₅ Ga 0. ₆₅ As intermediate Pando gap layer

A p-type GaAs contact layer (p = 7 × 10 ¹⁸ cm— ³ ) 312 (p = 1.5 × 10 ¹⁸ cm— ³ ) 311 and a thickness of 3.5 μπι were grown.

Thereafter, a p-side electrode 313 was deposited and the substrate was thinned to 100 μπι, and then an η-side electrode 314 was deposited and alloyed (FIG. 3 (f)). The wafer thus fabricated was cleaved and cut into chip pars so as to form a laser light emitting end face (primary cleavage). The resonator length at this time was 1000 μm. After asymmetric coating of a low-reflection film on the front end face and a high-reflection film on the rear end face, chips were separated by secondary cleavage. A semiconductor laser device was obtained by assembling the separated chips by junction _down.-In the above MOCVD method, trimethyl gallium (ΤMG), trimethyl indium (TMI) and trimethyl aluminum (TMA) were used as Group III raw materials. ), Arsine phosphine as a group V raw material, and hydrogen as a carrier gas. Dimethyl zinc (DMZ) was used as the p-type dopant, and disilane was used as the n-type dopant. Also, n-type A 1 Q. ₉ G a. During the growth of the s layer (ANDOP) 308, the HC 1 gas was converted to a HC 1/1 group molar ratio of 0.2 to suppress the deposition of poly on the SiN _x protective film. In particular, it was introduced so that the molar ratio of HC 1 / TMA was 0.22.

The fabricated semiconductor laser device was intermittently energized (CW) at 25 ° C to perform high-speed pulse measurement ( The current-light output and current-voltage characteristics obtained with a pulse width of 100 nsec and a duty of 50% were measured.

Fig. 5 shows the results. In the semiconductor laser device manufactured according to this example, in high-speed pulse measurement, the optical output increased with an increase in operating current, and no kink was generated up to 20 OmW, and high output characteristics were obtained. The semiconductor laser device of this example exhibited excellent characteristics with an oscillation wavelength of 667 nm on average, a threshold current of 37 mA, and a slope efficiency of 0.95 mW / mA on average. Furthermore, the semiconductor laser of the present invention has an average vertical divergence angle of 19 ° and a horizontal divergence angle of 8 °, and keeps the device resistance at about 5.5 Ω despite the thick p-side cladding layer. I was able to.

As described above, the semiconductor laser device of this embodiment can reduce the heat generation of the device due to the small passing resistance, and can perform stable operation for a long time at high temperature and high output (for example, 70 ° C, CW7 OmW). It is possible enough.

(Comparative Example 1)

Without forming the p-type third cladding layer (thickness: 1.2 μηι), a semiconductor laser device was fabricated by the same method as in Example 1 except for the current, light output, and current obtained by high-speed pulse measurement. The current-voltage characteristics were measured. The threshold current was as high as 75mA, and the slope efficiency was as low as 0.35mWZmA.

It is considered that the reason for the poor laser characteristics is that the leakage of light to the p-type contact layer has increased and the light loss has increased, that is, the waveguide loss has increased significantly.

(Comparative Example 2)-Without forming the p-type third cladding layer (thickness: 1.2 Am), the thickness of the p-type second cladding layer was set to 1.7 μni to compensate for the thickness, and the bottom of the ridge was formed. The semiconductor laser device was fabricated in the same manner as in Example 1 except that the width of the laser was 3 m (0.5 μπι wider than Example 1), and the current-light output and light output obtained by high-speed pulse measurement were Electric current Pressure characteristics were measured. No laser oscillation occurred in the obtained semiconductor laser device.

The reason for this is that the width of the top of the ridge was considerably narrowed down to 0.2 m, and the device resistance was considerably high (more than 20 Ω) due to side etching under the striped SiN _x protective film. Is thought to be the cause.

(Example 2)

p-type third cladding layer 310 thickness 0. 5 ^ πι of _{_{(A 1 0. 75 G a}} 0. 25) 0. 5 I n 0. 5 to P (p = 7 X l 0 18 cm one ³⁾ A semiconductor light emitting device was manufactured in the same manner as in Example 1 except for the change.

The initial characteristics were almost the same as in Example 1, but the element resistance was 8 Ω, which was slightly higher than in Example 1. The reason _{_{is, (A 10. 75 Ga .. 25}} ) 0. 5 I n 0. 5 P resistivities believed et al is due to greater than the resistivity of the p-type _{_{_{A 10. 8 Ga 0. 2 As}}} . (Example 3)

In this example, a self-pulsation type semiconductor laser device having the structure shown in FIG. 4 was manufactured. On a n-type GaAs (n = 1 x 10 ¹⁸ cm— ³ ) substrate 301 with a thickness of 350 and turned off by 10 ° from the (100) plane in the [011] direction, an n-type with a thickness of 1.2 μι _{_{_{(A 1 0. 7 Ga 0}}} . 3). · ₅ I η. _{· 5 P (n = 8 X} 10 17 cm one ^3, refractive index 3.2454) cladding layer _{_{302, (A 1 0, 5}} G a 0. 5) 0. 5 I n 0. 5 P light confining layer (non-doped ) 321, 0 a ₀ thickness _{_{511 «1. 5 I n 0}} . 5 P strained quantum well Toso (non-doped) 322, a thickness of _{_{5 nm (a 1 0. 5}} G a 0. 5) 0. 5 I n _0. _5? barriers layers (undoped) number of wells consisting of 323 is 6 Tajuuko well (MQW, n = 6) active layer 303, a thickness of 0. 08 μπι p-type (a 10. ₇ Ga ₀ _{_{_{. 3) 0. 5 I n}}} 0. 5 P (p = 1 X 10 18 cm- 3, the refractive index 3. p-type first cladding layer 304 made of 2454), the thickness of 5 nm of the p-type Ga _0. ₅ _{_{I n 0. 5 P (p}} = 1 X 10 18 cm -3) Tona Ru p-type etching stop layer 305, the thickness of 0.5 to _{_{5 m (a 1 0. 7}} Ga 0. 3) 0. ₅ I n. . ₅ P. (Z ^{n-doped: p = 1 X 10 18 cm-} 3, the refractive index 3. 2454) p-type second cladding layer 306 made of, thickness 0. 01 / xm of p-type (A 1 ₀ ₂ _{_{G a 0. 8) 0. 5}} I η 0. by _{5 Ρ (ρ = 1 Χ 10} 18 cm one ³⁾ sequentially product layer a p-type oxidation control layer 307 made of, to form a double-hetero structure ( Figure 4 (a)). Next, after depositing a 100-nm-thick SiNx protective film on the surface of this double heterosubstrate by plasma CVD, the [01-1] direction (the direction perpendicular to the off direction of the substrate) was changed by photolithography. A large number of SiNx protective films 351 having a stripe shape in the longitudinal direction were formed (FIG. 4B).

Next, the surface of the etching stop layer 305 was wet-etched using the striped SiNx protective film 351 so that the stripe width at the bottom of the ridge was 2.2. At this time, the width of the upper part of the ridge is 1.4 jum, the ridge shape is asymmetric, and the sum of the two base angles is 105 ° (one base angle is 62 °, the other base angle is 43 °) Met. (Fig. 4 (c)). At this time, a hydrochloric acid-based mixed solution and a sulfuric acid-based mixed solution were used as the wet-etching solution.

The removed portion by E Tsuchingu for ridge formation using S i Nx protective film 351 of the stripe by selective growth using an MOCVD method, a thickness of 0.4 111 11 type eight 1 _0. ₉ 0 & _{_0.1} 3 current blocking layer ^{(n = 2 X 10 18 cm-} 3, refractive Oriritsu 3.1590) 308 and a thickness of 0. 01 mu n-type _{_{m (a 1 0. 7 G}} a 0. 3 _{_{.) 0 5 I n 0:}} 5 P surface protective layer ^{(n = l X 10 18 cm-} 3) 309 was formed (FIG. 4 (d)). Thereafter, the striped SiNx protective film 351 is removed by a wet etching using a buffered hydrofluoric acid solution or a dry etching using a gas such as SF ₆ or CF ₄ (FIG. 4 (e)). p-type thickness 0. 5 m by MOCVD _{_{_{a 1 0. 8 G a 0}}} . 2 As third cladding layer ^{(p = l X 10 18 cm} "3, refractive index 3.2267) 31 0, thickness 0 . of 05μπι!) type _{_{_{A10. 35 Ga 0. 65 a}}} s intermediate Pando gap layer ^{(p = 1. 5X 10 18} cm- 3) 311 and the thickness 3. p-type 5 m G a a s contactors coat layer ( p = 7 × 10 ¹⁸ cm — ³ ) 312 was grown.

After this, the electrode 313 on the P side is deposited, and the substrate is thinned to 100 μπι. The side electrode 314 was deposited and alloyed (FIG. 4 (f)). The wafer thus fabricated was cleaved and cut into chip bars so as to form a laser light emitting end face (primary cleavage). The resonator length at this time was 300 μπι. After asymmetric coating of a low-reflection film on the front end surface and a high-reflection film on the rear end surface, the chip was separated by secondary cleavage. The separated chips were assembled at the junction down to obtain a semiconductor laser device. In the above MOCVD method, trimethyl gallium (ΤMG) and trimethyl indium (TMI) and trimethyl aluminum (TMA) are used as group III materials, arsine and phosphine are used as group V materials, and hydrogen is used as a carrier gas. Used. Dimethyl zinc (DMZ) was used as the p-type dopant, and disilane was used as the n-type dopant. Further, at the time of growth of the n-type A 10. ₉ Ga 0. s layer (and-loop) 308, in order to suppress the poly deposition on S i Nx protective film, moles of HC 1 gas HC 1 III Group The introduction was carried out so that the ratio was 0.2, especially the molar ratio of HC 1 ZTMA was 0.22.

Current-light output characteristics and current-voltage characteristics were measured by continuously applying current (CW) at 25 ° C to the fabricated semiconductor laser device.

As shown in Table 1 below, the semiconductor laser device of this example oscillates in vertical multimode as shown in FIG. 6 (a), and the visibility indicating coherence with return light is 0.25. It was found that low noise operation was possible without a high-frequency superimposing circuit. The lasing wavelength was 656 nm on average, the threshold current was 27 mA, and the operating current at 5 mW output was 31 mA, demonstrating excellent characteristics of low threshold and low operating current. Further, the vertical divergence angle of the semiconductor laser of the present invention is 37.5 ° on average and the horizontal divergence angle is 10.6 °, and the device resistance is 10 Ω despite the thick p-side cladding layer. It was able to be kept small. -As described above, the semiconductor laser device of the present embodiment can reduce the heat generation of the element due to the small passage resistance, and can realize a stable self-pulsation operation even at a high temperature of 75 ° C. or more. table 1

(Comparative Example 3)

without forming the p-type third cladding layer (thickness _0. 5 μ πι), others to produce a semiconductor laser device by the method same as in Example 3, current Ikko output obtained by high pulse measurement And the current-voltage characteristics were measured. The threshold current has increased to 60 mA.

It is considered that the cause of the deterioration of the laser characteristics in this way is that light leakage into the p-type contact layer is increased and light loss is increased, that is, waveguide loss is significantly increased.

(Comparative Example 4)

The same method as in Example 3 except that the thickness of the ρ-type second cladding layer was set to 1 μΐη to capture the P-type third cladding layer (thickness 0.5μπι) without affecting the thickness. The semiconductor laser device was manufactured by the method described above, and the current-light output characteristics and the current-voltage characteristics were measured. Laser oscillation did not occur in the obtained semiconductor laser device. The reason for this is that the width of the top of the ridge was considerably narrowed to 0.2 μm due to side etching under the striped Si Nx protective film, and the device resistance was considerably high (more than 20 Ω). It is thought that there is. (Example 4)

The p-type third cladding layer 310 thickness 0.5 // of _{_{m (A 1 0. 75 G}} a 0. 25) 0. 5 I n 0. 5 P (p = 7 X l 0 18 cm one ³⁾ A self-sustained pulsation type semiconductor laser device was manufactured in the same manner as in Example 3 except that the configuration was changed to.

The initial characteristics were almost the same as in Example 3, but the element resistance was 15 Ω, which was slightly higher than in Example 3, and no self-excited oscillation at 70 ° C was obtained. The cause _{_{is, (A l 0. 75 Ga}} 0. 25) 0. 5 I n 0. 5 p -type A 1 ₀ is the resistivity and the thermal resistance of the P. ₈ G a 0. ₂ As the resistivity and thermal This is considered to be because the heat generation of the element, that is, the temperature of the active layer was increased due to being larger than the resistance. (Example 5)

In this example, the self-pulsation type semiconductor laser device shown in FIG. 4 was manufactured. Thick 350 Myupaiiota from (100) plane [a 01 U direction 10 ° off the η-type ^{GaAs (n = 1 X 10 18} cm one ³⁾ on the substrate 301 by MOCVD, a thickness of 0. 5 mu m n-type ^{GaAs (n = 1 X 10 18} cm -3) ( not shown), having a thickness of 0. Ι μπι n-type _{Ga o. 5 I n 0.} 5 P (n = 1 X 10 18 cm "3) (not shown), the thickness of 1.6 // !!! type _{(a 1 o. 7 G a} o. 3) 0. 5 I n 0. 5 P (n = 8 X 10 17 cm- 3, refractive index 3.2454) cladding layer _{302, (a l o. 5} Ga 0. 5) 0. 5 I n 0. 5 P light confining layer (Nondo flop) 321, Ga thickness 5nm _{_0.} ₅ I n ₀ . ₅ P strained quantum well layer (undoped) 32 2, thickness 4. _{8 nm (a 1. · 5 Ga} 0. 5) 0. number of wells consisting of _₅ I _η ₀ · ₅ P barrier layer (non-doped) 323 a multiple quantum well (MQW, n = 8) There is a 8 active layer 303, the first thickness of 0 · 1 ^ 111) type _{_{_{(a 10. 7 Ga 0. 3}}} ). · 5 I n .. 5 P (p = 1 X 10 ¹⁸ cm one ^3, the first cladding layer 304 [rho type consisting refractive index 3 · 2.454), the thickness of 5 nm [rho Type _{_{_{Ga 0. 5 I n 0.}}} 5 P (p = 1 X 10 18 cm one ³⁾ p-type etching Sutotsu flop layer 305 consisting of, a thickness of _{_{0. 5 (A 1 0. 7}} G a 0. 3) . _{_{_{· 5 I n 0 5 P.}}} (Z n ^{-doped: ρ = 1 X 10 18 cm-} 3, the refractive index 3. 2454) p-type second cladding layer 30 6 made of, p-type thickness 0 · 01 (A _{_{_{_{10. 2 Ga 0. 8) 0}}}} . the _{_{_{5 I n 0. 5 P (}}} p = l X 10 18 cm- 3) by sequentially stacking a p-type oxidation control layer 307 made of, to form a double heterostructure (Figure 4 (a)). Next, a 100 nm-thick SiN x protective film is deposited on the surface of the double hetero substrate by plasma CVD, and then photolithography is performed in the [01-1] direction (a direction orthogonal to the off direction of the substrate). A large number of striped SiNx protective films 351 with () as the longitudinal direction were formed (Fig. 4 (b)).

Next, using the SiNx protective film 351 in the form of stripes, a wet etching was performed to the surface of the etching stop layer 305 so that the stripe width at the bottom of the ridge became 2.6 μπι. At this time, the width of the upper part of the ridge is 1.7 μπι, and the ridge shape is asymmetric, and the sum of the two base angles is 100 ° (the base angle of one side is 60 °, the base angle of the other side is 40 °) Met. (Fig. 4 (c)). At this time, the wet etching solution used was a hydrochloric acid-based mixed solution or a sulfuric acid-based mixed solution.

The portion removed by the etching for forming the ridge using the above-mentioned striped SiNx protective film 351 is selectively grown using the M.OCVD method to form an n-type A1 layer having a thickness of 0.4 jum. . · ₈₅ Ga _0. ₁₅ A s current blocking layer ^{(n = 2 X 10 18 cm-} 3, the refractive index 3.1924) 308 and a thickness of 0. 01 mu n-type _{_{m (A 1 0. 7 G}} a 0. _{_{_{3) 0.5 I 11 0. 5}}} ? surface protective layer ^{(11 = 1 X 10 18 cm-} 3) 309 was formed (FIG. 4 (d)). Thereafter, the striped SiNx protective film 351 is removed by a wet etching using a buffered hydrofluoric acid solution or a dry etching using a gas such as SF ₆ or CF ₄ (FIG. 4 (e)). p-type a 1 ₀ thickness 0. 5 m by MOCVD ₇₈ G a ₀ ₂₂ a s the third cladding layer.. (p - 1 X 10 18 cm- 3, the refractive index 3.2407) 310, thickness 0 . 05 πι of p-type _{_{_{_{A1 0. 35 Ga 0. 65}}}} As intermediate Pando gap layer ^{(p = 1. 5X 10 18 cm} ~ 3) 311 and the thickness 3 · [rho type GaAs con tact layer 5μηι (p = 7. X 10 ¹⁸ cm— ³ ) 312 was grown. Thereafter, a p-side electrode 313 was deposited and the substrate was thinned to 100 ηι, and then an n-side electrode 1114 was deposited and alloyed (FIG. 4 (f)). The wafer fabricated in this manner was cleaved and cut into chippers so as to form a laser light emitting end face (primary cleavage). The resonator length at this time was 300 ^ m. After asymmetric coating of a low-reflection film on the front end face and a high-reflection film on the rear end face, chips were separated by secondary cleavage. The separated chips were assembled in a junction down to obtain a semiconductor laser device. In the above MOCVD method, trimethylgallium (TMG), trimethylindium (TMI) and trimethylaluminum (TMA) are used as group III materials, arsine and phosphine are used as group V materials, and hydrogen is used as a carrier gas. Using. Dimethyl zinc (DMZ) was used as the p-type dopant, and disilane was used as the n-type dopant. Also n-type A1. ₉ G a. During growth of the s layer 308, a small amount of HC 1 gas was introduced to suppress poly deposition on the Si Nx protective film.

Current-light output characteristics and current-voltage characteristics were measured by continuously energizing (CW) the fabricated semiconductor laser device.

As shown in Fig. 13, the semiconductor laser device of this example oscillates vertically in multimode even at 75 ° C and 10 mW (peak wavelength 676.3 nm), showing a visibility that shows coherence with the return light. Is low at 0.34, which indicates that low-noise operation is possible without high-frequency superimposing circuits up to high temperatures (75 ° C or higher) and high outputs (1 OmW or higher).

(Example 6)

In this example, as shown in FIG. 4, a plurality of self-pulsation type semiconductor laser devices having different total active layer thicknesses were manufactured. On a η-type GaAs (n = 1 × 10 ¹⁸ cm— ³ ) substrate 301 with a thickness of 350 μπι and turned off by 10 ° in the [011] direction from the (100) plane, a 0.5 m η-type ^{GaAs (n = 1 X 10 18} cm- 3) ( not Shimese Figure), type 11 03 ₀ thickness _{_{0. 1 111. 5 I n 0}} . 5 P (n = 1 X 10 18 cm "3) (Figure Not shown), n-type (A1 o. ₇ G ao. J .. _{5 In} .. ₅ P (n = 8 × 10 ¹⁷ cm— ³ ) cladding layer 302, _{_{_{_{al 0. 5 Ga 0. 5}}}} ) 0. 5 I n 0. 5 P light confinement Me layer _{_{(non-doped) 321, Ga 0. 5 I}} n 0. 5 P strained quantum well layer (undoped) 3 22, the thickness of _{_{5 nm (a 1 0. 5}} Ga 0. 5) 0. 5 I n 0. 5 P Roh rear layer (non-doped) 323 consisting Tajuuko well (MQW) active layer 303, a thickness of 0. l / zm p type _{_{_{(a 10. 7 Ga 0. 3}}} ) 0. 5 I n 0. 5 P (p = l X 10 18 cm- 3) p -type first class head layer 304 made of, thickness 5 nm of the p-type _{_{_{Ga 0, 5 I n 0.}}} 5 P (p = 1 X 10 18 cm one ³⁾ p-type etching stop layer 305 made of, (a 10. ₇ having a thickness of 0. 5 / m G a 0. J o. _{_{_{. 5 I n 0 5 P (}}} Zn -doped: p = l X 10 ¹⁸ cm one ³⁾ p-type and a second clad layer 306, a thickness of 0. 01 μΐη p-type (a 1. · ₂ G a. · ₈₎ by _{_{_{_{0. 5 I n 0. 5}}}} P (p = 1 X 10 18 cm- 3) by sequentially stacking a p-type oxidation control layer 307 made of A double heterostructure was formed (Fig. 4 (a).) Next, a 100-nm-thick SiNx protective film was deposited on the surface of the double heterosubstrate by plasma CVD, and then photolithography was performed. [01-1] A large number of striped SiNx protective films 351 were formed with the direction (the direction perpendicular to the off direction of the substrate) as the longitudinal direction (FIG. 4 (b)).

Next, using the SiNx protective film 351 in the form of stripes, the surface of the etching stop layer 1305 was subjected to wet etching, so that the stripe width at the bottom of the ridge was 2.6 μΐη. At this time, the width of the upper part of the ridge was 1.7 m. (Fig. 4 (c)). At this time, a hydrochloric acid-based mixed solution or a sulfuric acid-based mixed solution was used as an etchant for wet etching.

The removed portion by E Tsuchingu for ridge formation using S i Nx protective film 351 of the stripe by selective growth using an MOCVD method, a thickness of 0. 4 μπι n-type A 1 _X G a preparative _X a s current blocking layer (x = 0. 85~0. 9, n = 2 X 10 18 cm- 3) 308 and the thickness 0.01 111 11 type _{_{(a 1 0. 7 G a}} 0. _{_{_{3) 0. 5 I n 0}}} . 5 P surface protective layer ^{(n = l X 10 18 cm-} 3) 309 was formed (FIG. 4 (d)). After that, the striped SiNx protective film 351 is removed using a buffered hydrofluoric acid solution or the like. Tsu preparative etching or SF _6, gas such as CF ₄ is removed by dry etching using (FIG. 4 (e)), 1 of a thickness of 0.5 111 Re-Pi MOCVD method) type eight 1 _{_0.} ₇₈ Ga _0. ₂₂ As third cladding layer ^{(p = l X 10 18 cm_} 3) 310, thickness ◦. 05 111 1) type eight _{_{_{1 0. 35 0 & 0.}}} 65 As intermediate Pando gap layer (p = l. 5 X 10 ¹⁸ cm- ³⁾ 311 and the thickness 3. [rho type 5 μπι G a a s contact layer (ρ = 7Χ 1 0 ¹⁸ cm one ³⁾ 312 were grown.

Thereafter, a p-side electrode 313 was deposited and the substrate was thinned to 100 μπι, and then an η-side electrode 314 was deposited and alloyed (FIG. 4 (f)). The wafer thus fabricated was cleaved and cut into chip bars so as to form a laser light emitting end face (primary cleavage). The resonator length at this time was 300 ^ m. After asymmetric coating of a low-reflection film on the front end face and a high-reflection film on the rear end face, the chips were separated by secondary cleavage. The separated chips were assembled at the junction down to obtain a semiconductor laser device. In the above MOCVD method, trimethylgallium (TMG) and trimethylindium (TMI) and trimethylaluminum (TMA) are used as group III materials, arsine phosphine is used as group V material, and hydrogen is used as carrier gas. Used. Dimethyl zinc (DMZ) was used as the p-type dopant, and disilane was used as the n-type dopant. In addition, the A 1 _X G as current blocking layer (x = 0.

85-0.9, η = 2 × 10 ¹⁸ cm— ³ ) During the growth of 308, HC 1 gas was introduced to suppress the deposition of poly on the SiNx protective film.

The current-optical output characteristics and the current-voltage characteristics were measured by continuously energizing (CW) the fabricated semiconductor laser device. As a result, the range of self-sustained pulsation (temperature and optical output) was too small for the number of Ido layers. It turned out to be strongly dependent on the total thickness of the active layer (the sum of the thicknesses of all the quantum well layers in the active layer). As shown in Fig. 14, self-oscillation at 25 ° C and 5 mW is possible when the total active layer thickness is '25 nm or more, and self-oscillation at 70 ° C and 5 mW when the active layer thickness is 30 nm or more. It became. In addition, self-oscillation at 75 ° C and 10 mW at 35 nm and above became possible. Therefore, the lower limit of the total thickness of the active layer is preferably 25 nm or more, more preferably 30 nm or more, and even more preferably 35 nm or more. Real truth When the active layer is strained as in the embodiment, the thickness is preferably not more than the critical thickness. That is, the upper limit of the total thickness of the active layer is preferably 80 nm or less, more preferably 60 nm or less, and even more preferably 50 nm or less. On the other hand, the upper limit of the total thickness of the active layer is preferably equal to or less than the thickness at which the quantum effect functions when the active layer has no strain. That is, the upper limit of the total active layer thickness is preferably 100 nm or less, more preferably 80 nm or less, and even more preferably 70 nm or less. Industrial applicability

INDUSTRIAL APPLICABILITY The semiconductor light emitting device of the present invention can be suitably used as a semiconductor laser having a low element resistance, a low pass resistance and a low thermal resistance and capable of high output operation. Lasers suitable as light sources for reading and writing optical discs, especially lasers for information processing and optical communication that require high output operation, lasers suitable for a wide range of applications such as information processing, optical communication, medical care, laser DDZ, etc. It can also be applied to light emitting diodes (LEDs) such as edge emitting type.

Further, according to the present invention, it is possible to provide a semiconductor laser device which has a small element resistance, a passing resistance, a thermal resistance and an operating current, and is capable of self-excited oscillation up to a high temperature. This self-pulsation type semiconductor laser device is resistant to the return light noise from the optical disk, so that a high-frequency superimposing circuit is not required in the device for reading the return optical disk, and it is possible to reduce the number of components and cost. It becomes. Further, it can be suitably used even when a light source having low coherence is required, such as for distance measurement.

Claims

The scope of the claims

1. a substrate, a first conductivity type cladding layer formed on the substrate, the first conductivity type cladding layer including at least one layer, an active layer formed on the first conductivity type cladding layer, and a first conductivity type cladding layer formed on the active layer. A second conductivity type first cladding layer, a second conductivity type second cladding layer having a stripe-shaped ridge structure formed on the second conductivity type first cladding layer, and a second conductivity type second cladding layer. A current blocking layer formed on the second conductive type first cladding layer so as to sandwich both sides of the ridge, and a current blocking layer on and near the ridge of the second conductive type second cladding layer; A semiconductor light-emitting device comprising at least a second-conductivity-type third cladding layer formed on the layer, and a trapezoidal cross section orthogonal to the stripe longitudinal direction of the ridge structure satisfying the following expression.

0.05 h / [(a + b) / 2] <0.5

2. The semiconductor light emitting device according to claim 1, wherein the cross-section is a trapezoid whose lower bottom is longer than the upper bottom.

3. The cross section is 0.4 at the top! 3. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device has a trapezoid having a trapezoid of about 4 μπι.

4. The semiconductor light emitting device according to any one of claims 1 to 3, wherein the cross section is a trapezoid having a height of 0.2 μηι to 1.5 μπι.

5. The semiconductor light emitting device according to any one of claims 1 to 4, wherein the shape of the cross section is asymmetrical.

6. A substrate, a first conductivity type cladding layer formed on the substrate, the first conductivity type cladding layer including at least one layer, an active layer formed on the first conductivity type cladding layer, and a first conductivity type cladding layer formed on the active layer. A second conductive type first clad layer, a second conductive type second clad layer having a stripe-shaped ridge structure formed on the second conductive type first clad layer, and a second conductive type second clad layer. A current blocking layer formed on the second conductive type first cladding layer so as to sandwich both side surfaces of the ridge; and a ridge of the second conductive type second cladding layer. And at least a second conduction type third cladding layer formed on the current blocking layer above and near the ridge, and has a single transverse mode oscillation in pulse driving at 25 ° C. Semiconductor light emitting device with a maximum light output of 80 mW or more.

7. The semiconductor light emitting device according to claim 6, wherein the light output density is 4 mW / μ.m ² or more.

8. The semiconductor light emitting device according to any one of claims 1 to 7, wherein the semiconductor light emitting device is a semiconductor laser device.

9. The semiconductor light emitting device according to any one of claims 1 to 5, wherein the semiconductor light emitting device is a self-pulsation type semiconductor laser device.

10. A substrate, a first conductivity type clad layer formed on the substrate, the first conductivity type clad layer comprising at least one layer, an active layer formed on the first conductivity type clad layer, and formed on the active layer A second conductive type first clad layer, a second conductive type second clad layer having a stripe-shaped ridge structure formed on the second conductive type first clad layer, and the second conductive type second clad layer A current blocking layer formed on the first cladding layer of the second conductivity type so as to sandwich both side surfaces of the ridge of the layer, and the current blocking layer on the ridge of the second cladding layer of the second conductivity type and in the vicinity of the ridge. At least 5 mW in single transverse mode oscillation in DC drive at 25 ° C. A semiconductor light emitting device, which is a self-excited oscillation type semiconductor laser device.

11. The semiconductor light emitting device according to claim 10, wherein the light output density is not less than 0. S mW / ^ um ² .

12. A substrate, a first-conductivity-type clad layer formed of at least one layer formed on the substrate, an active layer formed on the first-conductivity-type clad layer, and formed on the active layer A second conductive type first clad layer, a second conductive type second clad layer having a stripe-shaped ridge structure formed on the second conductive type first clad layer, and the second conductive type second clad layer A current blocking layer formed on the first cladding layer of the second conductivity type so as to sandwich both side surfaces of the ridge of the layer, and a lid of the second cladding layer of the second conductivity type. And a second conductive type third clad layer formed on the current blocking layer near the ridge and near the ridge, and is self-driven with an output of 5 mW or more at 70 ° C by DC driving. A semiconductor light emitting device, which is a self-excited oscillation type semiconductor laser device that oscillates.

13. The semiconductor light emitting device according to claim 12, wherein an oscillation threshold current at 25 ° C. by DC driving is 45 mA or less.

14. The semiconductor light emitting device according to any one of claims 1 to 13, wherein a thickness of the current blocking layer is smaller than a thickness of the second conductive type second cladding layer.

15. The semiconductor light emitting device according to claim 1, wherein a refractive index of the current blocking layer is smaller than a refractive index of the second conductive type second cladding layer.

16. The current blocking layer according to claim 1, wherein the current blocking layer is formed of a kind selected from the group consisting of AlGaInP, A1InP, AlGaAs, and A1GaAsP. The semiconductor light emitting device according to claim 1.

17. The semiconductor light emitting device according to any one of claims 1 to 16, wherein an oxidation suppression layer is provided on the ridge structure.

18. The semiconductor light emitting device according to claim 17, wherein said oxidation suppressing layer is made of a material having a band gap larger than a material of said active layer.

19. The semiconductor light emitting device according to any one of claims 1 to 18, wherein a refractive index of the second conductive type third quad layer is smaller than a refractive index of the second conductive type second quad layer. apparatus.

20. The semiconductor light emitting device according to any one of claims 1 to 19, wherein the resistivity of the third cladding layer of the second conductivity type is lower than the resistivity of the second cladding layer of the second conductivity type.

21. The semiconductor light emitting device according to any one of claims 1 to 20, further comprising a surface protection layer on the current blocking layer.

22. The semiconductor light emitting device according to claim 21, wherein the surface protective layer is made of a material having a larger band gap than a material of the active layer.

23. Previous | 5 Request for active layer containing saturable absorber in volume required for self-sustained pulsation The semiconductor light emitting device according to any one of Items 1 to 22.

24. The semiconductor light emitting device according to any one of claims 1 to 23, wherein the substrate has an off-angle from a plane equivalent to a (100) plane.

25. The semiconductor light emitting device according to any one of claims 1 to 24, wherein the cavity length is 150 / ζιη to 450 μm.

26. A substrate, a first-conductivity-type clad layer formed of at least one layer formed on the substrate, an active layer formed on the first-conductivity-type clad layer, and formed on the active layer A laminate comprising at least a second conductive type first clad layer and a second conductive type second clad layer formed on the second conductive type first clad layer is prepared. A stripe-shaped protective film is formed on the second conductive type second clad layer, and the second conductive type second clad layer is partially etched to form a stripe-shaped ridge on the second conductive type second clad layer. A current blocking layer is formed so as to sandwich both sides of the ridge of the second conductive type second cladding layer, the protective layer is removed, and the current blocking layer is formed on the ridge of the second conductive type second cladding layer. The third cladding of the second conductivity type is formed on the current blocking layer near the ridge. Comprising the step of forming a method of manufacturing a semiconductor light emitting device according to any one of claims first through 2 5 Section.

27. The method for manufacturing a semiconductor light emitting device according to claim 26, further comprising a step of forming a surface protective layer on said current blocking layer after forming said current blocking layer. .