JP2001015851A - Semiconductor laser device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser device which has a current constriction effect, a current confinement effect, and a light confinement effect, a high surge withstand voltage, and easy handle ability. SOLUTION: A semiconductor laser device 50 is equipped with a laminated structure composed of an N-type buffer layer 52, an N-type clad layer 53, an active layer 54, a P-type clad layer 55, a P-type intermediate layer 56, and a P-type cap layer 57 which are successively and epitaxially grown on an N-type substrate 51. The P-type intermediate layer 56 and the P-type can layer 57 above the P-type clad layer 55 are formed into a stripe 58 which serves as a current injection region. A Ti/Pt/Au multilayered material film is formed as a P-side electrode 59 extending over the P-type clad layer 55 and bestriding the P-type cap layer 57. The P-side electrode 59 is composed of a first electrode 59a which is in ohmic contact and a second electrode 59b which is in Schottky contact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device and a method of manufacturing the same, and more particularly, to a semiconductor laser device which has a high surge withstand voltage, operates stably, and is easy to handle, and a method of manufacturing the same. is there.

[0002]

2. Description of the Related Art Although there are various factors to be evaluated in the laser characteristics of a semiconductor laser device, energy efficiency or current efficiency is recognized as one of the important factors to be evaluated. Therefore, in order to improve energy efficiency, various current confinement structures, current confinement structures, or optical confinement structures have conventionally been formed as part of a double hetero (DH) junction stacked structure of a semiconductor laser device. Therefore, a laminated structure having a higher current confinement effect, current confinement effect, or light confinement effect has higher energy efficiency and is evaluated as a preferable laser resonator structure.

Here, a conventional basic structure for improving energy efficiency will be described with reference to FIGS. 9 to 11. FIG. The conventional semiconductor laser device 10 having the first structure is a semiconductor laser device having an energy efficiency structure in which ions are implanted into an upper cladding layer in a region other than the current injection region and the surface layer is converted into an insulating region. . As shown in FIG. 9, the semiconductor laser 10 includes an n-type buffer layer 12, which is epitaxially grown on an n-type compound semiconductor substrate 11 sequentially.
n-type cladding layer 13, active layer 14, p-type cladding layer 1
5 and a p-type cap layer 16.

[0004] The upper layer of the p-type cladding layer 15 and the p-type contact 16 at the center of the laminated structure are formed in a stripe shape connecting both end faces of the laser resonator structure as a current injection region. The p-type cladding layer 15 in a region excluding the current injection region
Is converted into an insulating region 17 having high electric resistance by ion implantation of ions such as protons (H).
An insulating film 18 is formed on the insulating region 17. As the p-side electrode 19, a multilayer metal film of Ti / Pt / Au is formed on the cap layer 16 and the insulating film 18, and is in ohmic contact with the cap layer 16. On the back surface of the substrate 11, a multilayer metal film of AuGe / Ni / Au is formed as the n-side electrode 20.

Conventional semiconductor laser device 22 of second structure
Is a semiconductor laser device having an energy efficiency structure having a ridge-shaped stripe as a current injection region and an insulating film in a region other than that region. As shown in FIG. 10, the semiconductor laser element 22 includes an n-type buffer layer 24, an n-type cladding layer 25, an active layer 26, a p-type cladding layer 27, which are sequentially epitaxially grown on an n-type compound semiconductor substrate 23. And a stacked structure of a p-type cap layer 28. The upper layer of the p-type clad layer 27 and the p-type contact 28 at the center of the laminated structure are formed as ridge-shaped stripes connecting both end faces of the laser resonator structure as current injection regions. An insulating film 29 is formed on the p-type cladding layer 27 in a region other than the current injection region so as to bury the ridge-shaped stripe. Ti as the p-side electrode 30
A / Pt / Au multilayer metal film is formed on the p-type cap layer 28 and the insulating film 29, and is in ohmic contact with the p-type cap layer 28. On the back surface of the substrate 23, a multilayer metal film of AuGe / Ni / Au is formed as the n-side electrode 31.

A conventional semiconductor laser device having a third structure 34
Is a semiconductor laser device having an energy efficiency structure having a ridge-shaped stripe as a current injection region and a current block layer formed by a pn junction in a region other than the region. As shown in FIG. 11, the semiconductor laser device 34 is composed of an n-type buffer layer 36, an n-type cladding layer 37, an active layer 38, and a p-type cladding layer 39 which are sequentially epitaxially grown on an n-type compound semiconductor substrate 35. Is provided. The upper part of the p-type cladding layer 39 at the center of the laminated structure is processed into a ridge-shaped stripe connecting both end faces of the laser resonator structure.
It is buried with, for example, an n-type GaAs layer that functions as a current blocking layer 40 by junction. On the striped p-type cladding layer 39 and the current blocking layer 40,
A p-type cap layer 41 is formed. As the p-side electrode 42, a multilayer metal film of Ti / Pt / Au is used as the cap layer 4.
1 and is in ohmic contact with the cap layer 41. On the back surface of the substrate 34, a multilayer metal film of AuGe / Ni / Au is formed as the n-side electrode 43.

The semiconductor laser devices having the first to third energy efficiency structures shown in FIGS. 9 to 11, respectively, have high effects of current confinement, current confinement, or light confinement. It is evaluated as an excellent laser resonator structure with high efficiency.

[0008]

However, the fact that the current confinement effect, current confinement effect, or light confinement effect at the time of current injection is high means that energy is concentrated in the stripe of the laser resonator structure. It is easy. Therefore, due to various unexpected factors,
When a phenomenon in which a large current suddenly flows through the laser resonator structure (hereinafter referred to as a surge) occurs, the current is concentrated on the stripe at a stretch, and as a result, light is concentrated on the active layer region below the stripe. Thus, phenomena such as end face destruction of the laser resonator structure or instantaneous optical damage are likely to occur. Furthermore, outside the stripe, the current is strongly blocked by forming an insulating film, forming an insulating film, forming a current blocking layer, and the like. I have.

That is, a semiconductor laser device having a structure with a high effect of current confinement, current confinement, or light confinement has a low surge withstand voltage on one side, and it is necessary to take measures against static electricity and surge caused by electric / electronic circuits. Therefore, it can be said that the semiconductor laser laser has low operation stability and is difficult to handle. On the other hand, in order to achieve a single transverse mode, a low operating current, a high output, and the like, it is necessary to perform current confinement and current / light confinement. Otherwise, for example, an optical pickup of an optical disk device Laser characteristics usually required for semiconductor lasers for laser printers or semiconductor lasers for laser printers cannot be satisfied. Therefore, the current confinement structure and the confinement structure of the laser resonator are basically necessary structures and cannot be largely changed.

As can be seen from the above description, a semiconductor laser device that satisfies both the provision of an energy efficiency structure having a current confinement effect, a current confinement effect, a light confinement effect, and the like, and a high surge withstand voltage is provided. It was not found in a conventional semiconductor laser device. Therefore, an object of the present invention is to solve such a problem and provide a semiconductor laser device having an energy efficiency structure having a current confinement effect, a current confinement effect, a light confinement effect, etc., and having a high surge withstand voltage and being easy to handle. To provide.

[0011]

In order to achieve the above object, a semiconductor laser device according to the present invention is characterized in that an electrode made of a metal film provided on a laminated structure of a compound semiconductor is formed on the uppermost layer of the laminated structure. It is characterized by comprising a first electrode portion that makes ohmic contact and a second electrode portion that makes Schottky contact with a layer having a low carrier concentration of a laminated structure.

The present invention can be applied to the composition of a compound semiconductor layer constituting a semiconductor laser without any limitation.
nP, AlGaAs, GaInAsP, AlGa
The present invention can be applied to a stacked structure of various compound semiconductor layers such as InAs, ZnSe, and GaN. The conductivity type of the uppermost layer where the first electrode portion makes ohmic contact and the conductivity type of the layer where the second electrode portion makes Schottky contact may be p-type or n-type. However,
It is desirable that both conductivity types be the same conductivity type, but the layer that makes Schottky contact is an i-layer (intrins) having a low concentration.
ic layer). Further, the electrode of the present invention may be a p-side electrode or an n-side electrode of a semiconductor laser device, and there is no restriction on the composition of the metal film. For example, a conventional Ti / Pt / Au multilayer metal film is used as the p-side electrode. It can be suitably used.

In the semiconductor laser device according to the present invention, with the above configuration, the first electrode portion in ohmic contact and the second electrode portion in Schottky contact have a voltage difference when a DC current flows. Is large, and the second electrode region in Schottky contact has a current blocking function. Therefore, during normal laser operation (during direct current driving), current is not injected from the second electrode portion. Instead, a current is injected into the current injection region (stripe portion) only from the first electrode portion in ohmic contact. Therefore, a good current confinement effect is exhibited. On the other hand, when an unexpected surge voltage (current) or the like is applied, the current also flows from the second electrode in Schottky contact, and the current hardly concentrates on the stripe portion. It is difficult to concentrate on the active layer region below the stripe. Therefore, no destruction of the end face at the time of surge occurs. During a surge, for example, a high-frequency current (voltage)
Is applied, and the Schottky contact area acts like a capacitor that easily passes high frequency components.
A state in which high-frequency current easily passes is obtained. That is, since the semiconductor laser device according to the present invention has a high surge withstand voltage, it can be evaluated that the semiconductor laser device has stable operation and is easy to handle.

In a preferred embodiment of the present invention, the first electrode portion is formed on a cap layer having a high carrier concentration provided as an uppermost layer of the ridge-shaped stripe formed in the laminated structure, and the second electrode portion is formed. The portion is formed on the upper clad layer having a lower carrier concentration than the cap layer provided along the stripe along the stripe. For example, in this embodiment, the carrier concentration of the cap layer is preferably about 1 × 10 ¹⁹ cm ⁻¹ or more, while the carrier concentration of the upper cladding layer is 5 × 10 ¹⁷ cm ⁻¹ or more and 2 × 10 ¹⁸ cm ^−1. The following range is preferable.

There is no restriction on the height of the ridge-shaped stripe. For example, a gain guide type laser having a low stripe ridge height, an index guide type laser etched to a position where a stripe ridge height is high and a refractive index difference with respect to laser light is sufficiently large, and conversely, A pulsation type laser in which the ridge height of the stripe is adjusted so that the difference in the refractive index is small or not so large may be used.

In a preferred embodiment of the present invention, both ends of the ridge-shaped stripe are formed in a tapered shape in which the stripe width is reduced from the center of the stripe toward the end face of the laser resonator structure. As a result, the current density inside the stripe can be reduced, so that the surge withstand voltage is further increased. In particular, the present invention can be suitably applied to a gain guide type laser in which a stripe shape design is important.

In another preferred embodiment of the present invention,
Both ends of the ridge-shaped stripe are formed in a flare shape in which the stripe width increases from the center of the stripe toward the end face of the laser resonator structure. This allows
Since the end face light density of the laser resonator structure can be reduced, the surge withstand voltage can be further increased. In particular, the present invention can be suitably applied to a high-efficiency index guide type laser having high current confinement and high light confinement.

In the present invention, the structure of the electrode is not limited as long as it has the first electrode portion and the second electrode portion. For example, the electrode made of a metal film may be replaced with the first electrode portion and the second electrode portion. In addition, a third electrode portion disposed on the upper cladding layer via an insulating film may be provided beside the second electrode portion.
In such an electrode structure, when the semiconductor laser element is mounted on the mounting substrate with the stripe surface facing the mounting substrate, the first electrode portion and the third electrode portion are substantially at the same height from the laser substrate. Becomes easier. In addition, the electrode made of a metal film may be a fourth electrode portion formed on a cap layer via an insulating film in addition to the first electrode portion and the second electrode portion. It may be provided in a region adjacent to the side of the second electrode portion. In such an electrode structure, when the semiconductor laser element is mounted on the mounting substrate with the stripe surface facing the mounting substrate, the first electrode portion and the third electrode portion are substantially at the same height from the laser substrate. Becomes easier.

The method for manufacturing a semiconductor laser device according to the present invention (hereinafter referred to as the first invention method) applied when manufacturing the above-described semiconductor laser device has a cap layer having a high carrier concentration as the uppermost layer. Forming a stacked structure on the compound semiconductor substrate, etching the stacked structure to form at least a cap layer in a ridge-shaped stripe and exposing the upper cladding layer beside the stripe, and Forming an electrode made of a metal film on the upper clad layer described above.

Another method for fabricating a semiconductor laser device according to the present invention (hereinafter referred to as a second invention method) applied to fabricating a semiconductor laser device having the above-mentioned third electrode portion is described in the uppermost layer. Forming a laminated structure having a cap layer having a high carrier concentration on a compound semiconductor substrate, and etching the laminated structure to form at least the cap layer in a ridge-like stripe and to expose an upper cladding layer beside the stripe. Forming an insulating film on the exposed upper cladding layer, excluding the upper cladding layer region along the stripe side, and forming the insulating film on the cap layer, on the exposed upper cladding layer and on the insulating film. Forming an electrode made of a metal film.

Another method for fabricating a semiconductor laser device according to the present invention (hereinafter referred to as a third invention method) applied to fabricating a semiconductor laser device having the above-mentioned fourth electrode portion is described in the uppermost layer. As a step of forming a laminated structure having a cap layer with a high carrier concentration on a compound semiconductor substrate, and excluding an edge in a direction perpendicular to a line connecting both end faces of the laser resonator structure, etching the laminated structure, Forming at least a cap layer in a ridge-like stripe and exposing the upper cladding layer in a region along the side of the stripe; forming an insulating film in a region except on the stripe and on the exposed upper cladding layer; Forming an electrode made of a metal film on the exposed upper cladding layer and the insulating film.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the accompanying drawings based on embodiments. Embodiment 1 This embodiment of the semiconductor laser device, an example embodiment of a semiconductor laser device according to the present invention, FIG. 1 is a sectional view showing a structure of a semiconductor laser device of the present embodiment. As shown in FIG. 1, the semiconductor laser device 50 of this embodiment is an n-type GaAs
An n-type GaInP buffer layer 52, an n-type AlGaInP cladding layer 53, an active layer 54 having a multiple quantum well structure (MQW) of GaInP, and a p-type AlGaInP cladding layer 5 are sequentially epitaxially grown on a substrate 51.
5, a stacked structure of a p-type Ga InP intermediate layer 56 and a p-type GaAs cap layer 57 is provided. p-type cladding layer 5
5, p-type Ga InP intermediate layer 56 and p-type GaAs
The cap layer 57 is formed as a ridge-like stripe structure (hereinafter simply referred to as a stripe portion) 58 connecting both end faces of the laser resonator structure, and serves as a current injection region of a laminated structure. Furthermore, as the p-side electrode 59, a Ti / Ti / Pt-type electrode extending over the p-type cladding layer 55 and then reaching the p-type cladding layer 55 and having a shape extending over the p-type cap layer 57. A multilayer metal film of Pt / Au is formed. On the back surface of the substrate 51, a multilayer metal film of AuGe / Ni / Au is formed as the n-side electrode 60.

In the semiconductor laser device 50 of this embodiment, the p-side electrode 59 is composed of a first electrode portion 59a in ohmic contact and a second electrode portion 59b in Schottky contact. I have. The first electrode portion 59a is
It is in ohmic contact with the p-type GaAs layer cap layer 72 having a high carrier concentration and formed as the uppermost layer of the stripe portion 58 serving as a current injection region. On the other hand, the stripe portion 5
In regions other than 8, the second electrode portion 59b is in contact with the p-type clad layer 55 having a low carrier concentration, and is not in ohmic contact but is in Schottky contact.

In the above electrode configuration, due to the difference in potential barrier between the ohmic contact and the Schottky contact, a current is injected only from the first electrode portion 59a at a certain voltage or less, and a first current at a certain voltage or more. The electrode part 59a and the second
Current is injected from both electrode portions 59b. That is, during normal laser operation (during direct current drive), current can be injected only into the ohmic contact stripe portion (current injection region) 58, and the device operates with good laser characteristics showing high current efficiency. On the other hand, when an unexpected surge voltage (current) or the like is applied, even in the Schottky contact region, the current flows, making it difficult for the current to concentrate on the stripe portion, and causing light to activate in the region immediately below the stripe portion. It becomes difficult to concentrate on the layer 54.
For example, when a high-voltage and high-frequency current (voltage) is applied, the Schottky contact region works like a capacitor that easily allows high-frequency components to pass through, so that a high-frequency current is easily passed. That is, since the surge withstand voltage of the semiconductor laser device is increased, the semiconductor laser device is easy to handle and has high operation stability.

In this embodiment, the stripe portion 5
Since 8 is not buried with an insulating film or the like, stress is unlikely to act on the stripe portion 58, and thus the operation reliability is excellent. In this embodiment, p outside the stripe portion 58
Although a gain guide type laser in which the etching depth of the mold cladding layer 55 is made shallow is assumed, the present invention can be applied to an index guide type laser, a pulsation type laser or the like by controlling the etching depth. For example,
If the etching depth is made sufficiently deep and etched to a position where the refractive index difference with respect to the laser beam becomes sufficiently large,
An index guide type laser can be manufactured.
If the etching depth is controlled so that the difference in the refractive index with respect to the laser beam is small or not so large, a pulsation laser can be obtained although the structure of the active layer needs to be taken into consideration. It should be noted that these types of semiconductor laser devices can be easily realized with an extremely general resonator design.

Embodiment of a method for forming a semiconductor laser device
One embodiment is an example of an embodiment in which the method for fabricating a semiconductor laser device according to the first invention method is applied to the fabrication of the semiconductor laser device 50 described above, and FIGS.
FIGS. 4A to 4C are cross-sectional views for respective steps when a semiconductor laser device is manufactured by the method of the embodiment. First, as shown in FIG. 2A, n is formed by an epitaxial growth method such as a MOCVD method.
An n-type GaInP buffer layer 52, an n-type AlGaInP cladding layer 53, and a GaI
Active layer 5 composed of nP multiple quantum well structure (MQW)
4, p-type AlGaInP cladding layer 55, p-type GaIn
The P intermediate layer 56 and the p-type GaAs cap layer 57 are epitaxially grown to form a laminated structure of the semiconductor laser.

Next, as shown in FIG. 2B, the p-type cap layer 57 and the p-type Ga
By etching the upper layer of the InP intermediate layer 56 and the p-type clad layer 55, the upper layer of the p-type clad layer 55 and the p-type GaI
The stripe portion 58 including the nP intermediate layer 56 and the p-type cap layer 57 is formed, and the p-type cladding layer 55 is exposed on both sides of the stripe portion 58. In this embodiment, the stripe shape is a straight shape with a constant stripe width, as shown in FIG.

Next, a multilayer metal film of Ti / Pt / Au is vapor-deposited on the entire surface of the substrate so as to extend over the p-type cladding layer 55 from above the p-type cladding layer 55 through the stripe portion 58. Then, the p-side electrode 5 is etched by etching the multilayer metal film.
9 is further formed, and AuGe / Ni / A
u multilayer metal film is formed and patterned to form an n-side electrode 6.
0 is formed. Thus, the semiconductor laser device 50 shown in FIG. 1 can be manufactured.

According to the method of the present embodiment, as described above, the semiconductor laser device 50 can be manufactured by an extremely simple process. Therefore, the conventional semiconductor laser device can be manufactured in terms of product yield and manufacturing cost. This is advantageous as compared with a method for manufacturing an element.

Modification of the semiconductor laser device of the first embodiment
One modified example is a modified example of the semiconductor laser device 50 of the first embodiment, and FIGS. 3A and 3B are a perspective view and a top view of the semiconductor laser device of the modified example, respectively. .
In the semiconductor laser device 62 of this modification, instead of the slate shape of the stripe portion 58 of the semiconductor laser device 50 of the first embodiment, a stripe portion 63 is formed as shown in FIGS. 3A and 3B. Central part 63a with straight shape
And tapered portions 63b provided at both end portions of the stripe portion 68, the width of the stripe being reduced from the central portion 63a toward the front end. The semiconductor laser device 62 of this modification example has a stripe portion 73
Since the current density inside the stripe can be reduced by forming the tapered portions 63b at both ends, the surge withstand voltage can be further increased as compared with the semiconductor laser device 50 of the first embodiment. In particular, the present invention can be suitably applied to a gain guide type laser in which a stripe shape design is important.
The structure of the first modification can be easily realized without basically changing the manufacturing process of the first embodiment.
It can be said that the structure is as simple as.

Modification of the semiconductor laser device of Embodiment 1
The two modifications are modifications of the semiconductor laser device 50 of the first embodiment, and FIGS. 4A and 4B are a perspective view and a top view of the semiconductor laser device of the modification, respectively. .
In the semiconductor laser device 64 of this modification, instead of the slate shape of the stripe portion 58 of the semiconductor laser device 50 of the first embodiment, a stripe portion 65 is formed as shown in FIGS. 4A and 4B. Central part 65a with straight shape
And flare portions 65b provided at both end portions of the stripe portion 65, and the width of the stripe increases from the central portion 65a toward the front end. In the semiconductor laser element 64 of this modification, the end face light density of the laser resonator structure can be reduced by forming the both ends of the stripe portion 65 into flared portions 65b in connection with the transverse mode design and the end face light density design. Therefore, the semiconductor laser device 50 of the first embodiment
The surge withstand voltage can be further increased as compared with. In particular, the present invention can be suitably applied to a high-efficiency index guide type laser having high current confinement and light confinement.
The structure of the first modification can be easily realized without basically changing the manufacturing process of the first embodiment.
It can be said that the structure is as simple as.

Second Embodiment of Semiconductor Laser Device This embodiment is another example of the embodiment of the semiconductor laser device according to the present invention, and FIG. 5 shows the configuration of the semiconductor laser device of this embodiment. It is sectional drawing. As shown in FIG. 5, the semiconductor laser element 68 of the present embodiment is an n-type GaAs
n sequentially grown epitaxially on the s-substrate 69
-Type GaInP buffer layer 70, n-type AlGaInP cladding layer 71, GaInP multiple quantum well structure (MQW)
Active layer 72 made of p-type AlGaInP clad layer 7
3, a stacked structure of a p-type Ga InP intermediate layer 74 and a p-type GaAs cap layer 75.

At the center of the laminated structure, the p-type cladding layer 7
3, the p-type intermediate layer 74 and the p-type cap layer 75
It is formed as a stripe portion 76 and serves as a current injection region of a laminated structure. The p-type cladding layer 73 is exposed in a region along the stripe portion 76 on both sides of the stripe portion 76, and in a region outside the exposed region of the p-type cladding layer 73, the insulating film, for example, the SiO ₂ film 77 is p-type. Clad layer 7
3 is formed. Then, covering the SiO ₂ film 77, the p-type cladding layer 73, and the stripe portion 76,
An i / Pt / Au multilayer metal film is formed as the p-side electrode 78. On the back surface of the substrate 69, an n-side electrode 7 is provided.
As No. 9, a multilayer metal film of AuGe / Ni / Au is formed.

In the semiconductor laser device 68 of this embodiment, the p-side electrode 78 has the first electrode portion 78a in ohmic contact, the second electrode portion 78b in Schottky contact, and the SiO ₂ film. 77 and a third electrode portion 78c on the substrate 77. The first electrode portion 78a is in ohmic contact with the p-type GaAs layer cap layer 75 having a high carrier concentration and formed as the uppermost layer of the stripe portion 76 serving as a current injection region. On the other hand, in the regions on both sides of the stripe portion 76, the second electrode portion 78b is in contact with the p-type cladding layer 73 having a low carrier concentration, and is not in ohmic contact but is in Schottky contact.

Therefore, in the semiconductor laser device 68 of the present embodiment, similarly to the semiconductor laser device 50 of the first embodiment, due to the difference in the potential barrier, the current injection region which is in ohmic contact during normal laser operation is operated. Current can be injected only into the current, and current constriction is performed. Also, p
Due to the presence of the region in Schottky contact with the side electrode 78, similar to the semiconductor laser device 50 of the first embodiment,
The structure has a high surge withstand voltage.

Unlike the first embodiment, in the present embodiment, an insulating film 77 is formed on both sides of the stripe portion 76, and the first electrode portion 78a and the first electrode portion 78a in which the p-side electrode 78 makes ohmic contact are formed. In addition to the second electrode portion 78b in Schottky contact, the third electrode portion 7 is further formed on the insulating film 77.
8c. Accordingly, in the present embodiment, the third electrode portion 78c is connected to the first electrode portion 78 of the stripe portion 76.
Since the height is almost the same as the height a, it is difficult for unnecessary force to act on the stripe portion 76 when soldering is performed on the stripe surface and mounted on the mounting board, and assembling stability and reliability are improved. Etc. can be expected. In this embodiment, as in the first and second modifications of the first embodiment, both ends of the stripe portion 76 can be tapered and flared without changing the process.

Embodiment of a method for manufacturing a semiconductor laser device
The second embodiment is an example of an embodiment in which the method of manufacturing a semiconductor laser device according to the second invention method is applied to the above-described semiconductor laser device 68. FIGS. FIGS. 4A and 4B are cross-sectional views for respective steps when a semiconductor laser device is manufactured by the method of the embodiment. In this embodiment, first, as shown in FIG. 6A, an n-type GaInP buffer layer 70 and an n-type AlGaIn are sequentially formed on an n-type GaAs substrate 69 by an epitaxial growth method such as a MOCVD method.
P cladding layer 71, GaInP multiple quantum well structure (M
QW) active layer 72, p-type AlGaInP cladding layer 73, p-type GaInP intermediate layer 74, and p-type GaAs
The s cap layer 75 is epitaxially grown to form a laminated structure of the semiconductor laser.

Next, as shown in FIG. 6B, the p-type cap layer 75 and the p-type Ga
The upper layer of the p-type clad layer 73 and the p-type GaI
The stripe portion 76 including the nP intermediate layer 74 and the p-type cap layer 75 is formed, and the p-type cladding layer 73 is exposed on both sides of the stripe portion 76. In the present embodiment, the stripe portion 76 has a straight shape with a constant stripe width.

Next, an SiO ₂ film is formed on the entire surface of the substrate, and the p-type cap layer 75 on the stripe portion 76 and the p-type cladding layer 73 on both sides of the stripe portion 76 are exposed along the stripe portion 76. In addition, patterning is performed so that the SiO ₂ film 77 is formed in a region separated from the stripe portion 76. Next, a multilayer metal film of Ti / Pt / Au is deposited on the entire surface of the substrate, and from the SiO ₂ film 77 on the p-type cladding layer 73, on the stripe portion 76, and on the p-type cladding layer 73.
The p-side electrode 78 is formed by etching the multi-layered metal film so as to reach the SiO ₂ film 77 through the above step, and a multi-layered metal film of AuGe / Ni / Au is formed on the back surface of the substrate 69 and patterned. An n-side electrode 79 is formed. This allows
The semiconductor laser device 68 shown in FIG. 5 can be manufactured.

Third Embodiment of Semiconductor Laser Device This embodiment is still another example of the embodiment of the semiconductor laser device according to the present invention, and FIG. 7 shows the configuration of the semiconductor laser device of this embodiment. FIG. As shown in FIG. 7, the semiconductor laser device 80 of the present embodiment has an n-type G
An n-type GaInP buffer layer 82 and an n-type AlGaIn are sequentially epitaxially grown on an aAs substrate 81.
P cladding layer 83, multiple quantum well structure of GaInP (M
QW) active layer 84, p-type AlGaInP cladding layer 85, p-type Ga InP intermediate layer 86, and p-type GaAs
The s cap layer 87 has a laminated structure.

In the center of the laminated structure, the p-type cladding layer 8
5, the p-type intermediate layer 86 and the p-type cap layer 87
It is formed as a stripe portion 88 and serves as a current injection region of a laminated structure. A mesa 89 having the same structure is formed in a region separated from the stripe 88 on both sides of the stripe 88, and the p-type cap layer 8 of the mesa 89 is formed.
An insulating film, for example, an SiO ₂ film 90 is formed on the top and the side walls. Between the stripe portion 88 and the mesa portion 89, the p-type cladding layer 85 is exposed along the stripe portion 88. Then, Ti / Pt / A covering the SiO ₂ film 90, the p-type cladding layer 85, and the stripe portion 88.
A multilayer metal film of u is formed as a p-side electrode 91. Also, on the back surface of the substrate 81, as an n-side electrode 92,
A multilayer metal film of AuGe / Ni / Au is formed.

In the semiconductor laser device 80 of this embodiment, the p-side electrode 91 has the first electrode portion 91a in ohmic contact, the second electrode portion 91b in Schottky contact, and the SiO ₂ film. And a fourth electrode portion 91c on the upper electrode 90. The first electrode portion 91a is in ohmic contact with the p-type GaAs layer cap layer 87 having a high carrier concentration and formed as the uppermost layer of the stripe portion 88 serving as a current injection region. On the other hand, in the region between the stripe portion 88 and the mesa portion 89, the second electrode portion 91b is in contact with the p-type cladding layer 85 having a low carrier concentration.
It is not an ohmic contact but a Schottky contact.

Therefore, in the semiconductor laser device 80 of the present embodiment, similarly to the semiconductor laser device 50 of the first embodiment, due to the difference in the potential barrier, the current injection region that is in ohmic contact during normal laser operation is operated. Current can be injected only into the current, and current constriction is performed. Also, p
Due to the existence of the region in Schottky contact with the side electrode 91, as in the case of the semiconductor laser device 50 of the first embodiment,
The structure has a high surge withstand voltage. Note that, in the present embodiment, similarly to the first and second modifications of the first embodiment, the stripe portions 76 are not changed without any process.
Can be tapered and flared at both ends.

Further, in the present embodiment, the mesa portions 89 are formed on both sides of the stripe portion 88 and are substantially the same height as the stripe portion 89.
Similarly to the above, when soldering is performed on the stripe surface and mounted on the mounting substrate, unnecessary force hardly acts on the stripe portion 88, and improvement in assembly stability and reliability can be expected. In this embodiment, when the etching depth is deep,
That is, even when the height of the stripe portion 88 is high, the insulating film 9
By adjusting the film thickness of 0, it is easier to form the outer height of the stripe portion 88 at the same height as the stripe portion 88 than in the second embodiment.

Embodiment of a method for manufacturing a semiconductor laser device
The third embodiment is an example of an embodiment in which the method for manufacturing a semiconductor laser device according to the third invention method is applied to the above-described semiconductor laser device 80. FIGS. 8A to 8C show this embodiment. FIG. 9 is a cross-sectional view for each step when a semiconductor laser element is manufactured by the method of the embodiment. In this embodiment, first, FIG.
As shown in FIG. 1A, an n-type GaInP buffer layer 82, an n-type AlGaInP cladding layer 83, and a multiple quantum well structure (MQW) of GaInP are sequentially formed on an n-type GaAs substrate 81 by an epitaxial growth method such as the MOCVD method. Active layer 84, p-type AlGaInP cladding layer 8
5. The p-type GaInP intermediate layer 86 and the p-type GaAs cap layer 87 are epitaxially grown to form a stacked structure of the semiconductor laser.

Next, as shown in FIG. 8B, the p-type cap layer 87 and the p-type Ga
By etching the upper layer of the InP intermediate layer 86 and the p-type clad layer 85, the upper layer of the p-type clad layer 85, the p-type GaI
A stripe portion 88 composed of an nP intermediate layer 86 and a p-type cap layer 87, and mesas 89A and 89B having the same layer structure formed on both sides of the stripe 88 are formed. During this time, the p-type cladding layer 85 is exposed. In the present embodiment, the stripe portion 8
8 has a straight shape with a constant stripe width.

Next, an SiO ₂ film is formed on the entire surface of the substrate and patterned to form an SiO ₂ film 90 on the p-type cap layer 87 of the mesa 89 and on the side walls. Next, a multilayer metal film of Ti / Pt / Au is deposited on the entire surface of the substrate, and the mesa unit 8 is formed.
The multi-layered metal film is etched so as to reach the SiO ₂ film 90 of the mesa portion 89b from the 9A SiO ₂ film 90 through the p-type cladding layer 85, the stripe portion 88, and the p-type cladding layer 85. A p-side electrode 91 is formed, and a multilayer metal film of AuGe / Ni / Au is formed on the back surface of the substrate 81, and is patterned to form an n-side electrode 92. Thus, the semiconductor laser device 80 shown in FIG. 7 can be manufactured.

In the description of the first to third embodiments of the semiconductor laser device and the method of manufacturing the same, AlGaInP
The present invention has been described by taking an example of a semiconductor laser device of the AlGas type, the GaInAsP type, and the AlGas type.
The present invention can be easily applied to semiconductor laser devices of various composition systems such as InAs, ZnSe, and GaN. Further, the present invention can be applied to various laser structures different from those of the embodiment and a manufacturing method thereof without departing from the gist of the present invention.

[0049]

According to the present invention, an electrode made of a metal film, which is provided on a laminated structure of a semiconductor laser, has a first electrode portion in ohmic contact with the uppermost layer of the laminated structure, and a carrier concentration of the laminated structure. The following effects can be obtained by using the low electrode layer and the second electrode portion in Schottky contact. Since the voltage difference between the first electrode portion in ohmic contact and the second electrode portion in Schottky contact when a DC current flows is large, during normal laser operation (during DC current driving), Current flows only in the first electrode portion in ohmic contact, and the device operates with good laser characteristics with a large current confinement effect. On the other hand, when an unexpected surge or the like is applied, current is also injected from the second electrode portion that makes Schottky contact, so that it is difficult for the current to concentrate on the stripe portion. That is, the surge withstand voltage of the semiconductor laser element is increased, and the laser is easy to handle and has high operation stability. For example, at the time of a surge in which a high-frequency current (voltage) is applied, the second electrode portion functions like a capacitor that easily passes a high-frequency component, and the high-frequency current easily passes. Furthermore, the surge withstand voltage can be further increased by making the end portion of the stripe portion tapered or flared. In addition, the method of the present invention realizes a method of manufacturing a semiconductor laser device according to the present invention with a small number of process steps, and has a simple device structure and process. It is better than that.

[Brief description of the drawings]

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

FIGS. 2A to 2C are cross-sectional views for respective steps when a semiconductor laser device is manufactured by the method of the first embodiment.

FIGS. 3 (a) and 3 (b) show Modification Example 1, respectively.
3 is a perspective view and a top view of the semiconductor laser device of FIG.

FIGS. 4 (a) and (b) show modified example 2 respectively.
3 is a perspective view and a top view of the semiconductor laser device of FIG.

FIG. 5 is a cross-sectional view illustrating a configuration of a semiconductor laser device according to a second embodiment.

FIGS. 6A to 6C are cross-sectional views for respective steps when a semiconductor laser device is manufactured by the method of the second embodiment.

FIG. 7 is a cross-sectional view illustrating a configuration of a semiconductor laser device according to a third embodiment.

FIGS. 8A to 8C are cross-sectional views of respective steps when a semiconductor laser device is manufactured by the method of Embodiment 3;

FIG. 9 is a cross-sectional view showing a configuration of a conventional semiconductor laser device having a first structure.

FIG. 10 is a sectional view showing a configuration of a conventional semiconductor laser device having a second structure.

FIG. 11 is a sectional view showing a configuration of a conventional semiconductor laser device having a third structure.

[Explanation of symbols]

10: a conventional semiconductor laser device having the first structure, 11:
... n-type compound semiconductor substrate, 12 ... n-type buffer layer, 1
3 ... n-type cladding layer, 14 ... active layer, 15 ... p-type cladding layer, 16 ... p-type cap layer, 17 ... insulating region, 18 ... insulating film, 19 ... p-side electrode, 20 …… n
Side electrode, 22: conventional semiconductor laser device of second structure, 23: n-type compound semiconductor substrate, 24: n-type buffer layer, 25: n-type cladding layer, 26: active layer, 2
7 p-type cladding layer, 28 p-type cap layer, 29
... Insulating film, 30 p-side electrode, 31 n-side electrode, 3
4 ... the conventional semiconductor laser device having the third structure, 35 ...
n-type compound semiconductor substrate, 36... n-type buffer layer, 37
... n-type cladding layer, 38 ... active layer, 39 ... p-type cladding layer, 40 ... current blocking layer, 41 ... p-type cap layer, 42 ... p-side electrode, 43 ... n-side electrode, 50 ...
... the semiconductor laser device of the first embodiment, 51 ... n-type Ga
As substrate, 52... N-type GaInP buffer layer, 53.
... n-type AlGaInP cladding layer, 54 ... GaInP
, An active layer comprising a multiple quantum well structure (MQW) of
... p-type AlGaInP cladding layer, 56 ... p-type GaI
nP intermediate layer, 57 ... p-type GaAs cap layer, 58 ...
... Stripe portion, 59 ... p-side electrode, 59a ... first electrode portion, 59b ... second electrode portion, 60 ... n-side electrode
62: semiconductor laser element of Modification 1; 63: stripe portion; 63a: central portion; 63b: taper portion;
... Semiconductor laser element of Modification 2 65, Stripe portion 65a Central portion 65b Flare portion 68
... The semiconductor laser device of the second embodiment, 69... N-type Ga
As substrate, 70... N-type GaInP buffer layer, 71.
... n-type AlGaInP cladding layer, 72 ... GaInP
, An active layer consisting of a multiple quantum well structure (MQW)
... p-type AlGaInP cladding layer, 74 ... p-type GaI
nP intermediate layer, 75 ... p-type GaAs cap layer, 76 ...
... stripe portion, 77 ...... SiO ₂ film, 78 ...... p-side electrode, 78a ...... first electrode portion, 78b ...... second electrode portion, 78c ...... third electrode portions, 79 ...... n-side Electrode, 80
... The semiconductor laser device of Embodiment 3 81, n-type G
aAs substrate, 82... n-type GaInP buffer layer, 83
... N-type AlGaInP cladding layer, 84.
Active layer composed of P multiple quantum well structure (MQW), 85
... P-type AlGaInP cladding layer, 86 p-type Ga
InP intermediate layer, 87 p-type GaAs cap layer, 88
...... Stripe part, 89 ... Mesa part, 90 ... SiO ₂
Film, 91... P-side electrode, 91 a.
b... second electrode portion, 91 c... fourth electrode portion, 92.
... n-side electrode.

Claims (9)

[Claims] An electrode comprising a metal film provided on a layered structure of a compound semiconductor has a first electrode portion in ohmic contact with an uppermost layer of the layered structure; And a second electrode portion in contact with the semiconductor laser device. A first electrode portion formed on a cap layer having a high carrier concentration provided as an uppermost layer of the ridge-shaped stripe formed in the laminated structure;
2. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is formed on an upper clad layer having a lower carrier concentration than a cap layer provided along the stripe along the stripe. 3. The ridge-shaped stripe according to claim 2, wherein both end portions of the ridge-shaped stripe are formed in a tapered shape in which a stripe width is reduced from a center portion of the stripe toward an end face of the laser resonator structure. 14. The semiconductor laser device according to claim 1. 4. The ridge-shaped stripe according to claim 2, wherein both end portions of the ridge-shaped stripe are formed in a flare shape in which the stripe width increases from the center of the stripe toward the end face of the laser resonator structure. 14. The semiconductor laser device according to claim 1. 5. An electrode made of a metal film includes a third electrode portion disposed on an upper clad layer via an insulating film in addition to the first electrode portion and the second electrode portion. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is provided beside the electrode portion. 6. An electrode made of a metal film includes a first electrode portion and a second electrode portion, and a fourth electrode portion formed on a cap layer with an insulating film interposed between the first electrode portion and the second electrode portion. 3. The semiconductor laser device according to claim 2, wherein the semiconductor laser device is provided in a region adjacent to the side of the part. 7. A step of forming a stacked structure having a cap layer having a high carrier concentration as a top layer on a compound semiconductor substrate, and etching the stacked structure to form at least the cap layer in a ridge-like stripe and at the same time beside the stripe. A method for manufacturing a semiconductor laser device, comprising: an etching step of exposing an upper clad layer; and a step of forming an electrode made of a metal film on the cap layer and on the exposed upper clad layer. 8. A step of forming a laminated structure having a cap layer having a high carrier concentration as the uppermost layer on a compound semiconductor substrate, and etching the laminated structure to form at least the cap layer in a ridge-like stripe and to form a horizontal stripe. An etching step of exposing the upper cladding layer, a step of forming an insulating film on the exposed upper cladding layer except for an upper cladding layer region along the side of the stripe, and a step of exposing the upper cladding on the cap layer Forming an electrode made of a metal film on the layer and on the insulating film. 9. A method of forming a stacked structure having a cap layer having a high carrier concentration as a top layer on a compound semiconductor substrate, and excluding an edge in a direction perpendicular to a line connecting both end faces of the laser resonator structure. Etching the laminated structure to form at least a cap layer in a ridge-like stripe and exposing the upper cladding layer in a region along the stripe side; and forming an insulating film in a region except on the stripe and the exposed upper cladding layer. A method for manufacturing a semiconductor laser device, comprising: a forming step; and a step of forming an electrode made of a metal film on a cap layer, an exposed upper cladding layer, and an insulating film.