JPH114041A - Manufacture of semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a ridge and a high-resistance region to be formed at the same time by a method wherein a contact layer and the upper part of an upper clad layer are selectively dry-etched into a ridge by the use of methane gas and hydrogen gas, and furthermore an electrode metal is formed covering the contact layer. SOLUTION: A lower clad layer 1a, an active layer 2, an upper clad layer 3, and a contact layer 4 are grown in crystal on a semiconductor substrate 1 through an MOCVD method or the like, and an insulating film 5 which is a few 7 μm or so wide extending like a ridge is formed on the contact layer 4, and the semiconductor substrate 1 is subjected to dry etching by the use of methane gas and hydrogen gas using the insulating film 5 as a mask, whereby the contact layer 4 and the upper part of the upper clad layer 3 are selectively etched into a ridge 10. Furthermore, the insulating film 5 is removed by etching, and an electrode metal 7 is formed covering the upper clad layer 3 and the contact layer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor laser, and more particularly, to a method for manufacturing a semiconductor laser having a ridge.

[0002]

2. Description of the Related Art FIG. 2 is a view showing a method of manufacturing a conventional ridge type semiconductor laser. In FIG.
s, a lower clad layer made of n-type AlGaAs, 2 an active layer having a quantum well structure in which AlGaAs layers and GaAs layers are alternately laminated, 3
Is an upper cladding layer made of p-type AlGaAs, 4 is a contact layer made of p-type GaAs, 5 is SiON or SiO which is a mask for forming a ridge by etching.
₂ , an insulating film made of SiN or the like, 6 an insulating film made of SiON, SiO ₂ , SiN or the like for confining current, 7 an electrode metal serving as a p-side electrode, 8 an electrode metal serving as an n-side electrode, 10 Is a ridge.

Next, a method for manufacturing a conventional semiconductor laser will be described. First, a lower cladding layer 1a having a thickness of about 1 to 2 μm and an active layer 2 having a thickness of about 0.1 μm are formed on a semiconductor substrate 1.
Upper clad layer 3 having a thickness of about 2 μm, thickness of about 0.5 to
A 3 μm contact layer 4 is grown by MOCVD or the like (FIG. 2A).

Next, a thickness of about 200 is formed on the contact layer 4.
After forming an insulating film of up to several thousand angstroms, the insulating film is patterned using a photolithography technique or the like, and a stripe having a width substantially equal to the width of a ridge formed in a subsequent process, that is, a width of approximately several μm. Insulating film 5 extending in a shape
Is formed (FIG. 2B).

Subsequently, selective etching is performed on the contact layer 4 and the upper cladding layer 3 using the insulating film 5 as a mask so that the remaining thickness of the upper cladding layer 3 is about 0.1 to 0.5 μm. To form a ridge 10 (FIG. 2).
(c)).

Further, the insulating film 5 is dry-etched.
After the removal, an insulating film 6 is formed on the surfaces of the contact layer 4 and the upper cladding layer 3 (FIG. 2D). This thickness may range, for example, from hundreds to thousands of angstroms. Then, the insulating film 6 is removed only on the ridge 10 to expose the contact layer 4 (FIG. 2E).

Subsequently, an electrode metal 7 is formed on the entire upper surface of the substrate 1 so as to cover the insulating film 6 and the contact layer 4 exposed on the ridge 10, and an electrode metal 8 is formed on the back surface of the substrate 1. Then, a laser cavity end face is formed by cleavage or the like to obtain a semiconductor laser as shown in FIG.

Next, the operation will be described. When a current is injected into the semiconductor laser manufactured as described above between the electrodes via the electrode metals 7 and 8, the current is squeezed through the ridge from above the ridge from which the insulating film 6 has been removed, and the active layer 2 is formed. And a certain current value according to the gain of the active layer 2,
That is, when a current equal to or more than the threshold current flows, laser oscillation occurs.

[0009]

As described above, in the conventional semiconductor laser having a ridge, the current is injected only from the upper portion of the ridge 10 into the ridge 10 by providing the insulating film 6 in which only the upper portion of the ridge 10 is removed. As a possible structure, the current can be narrowed and injected into the active layer 2.

However, as described above, the current is supplied to the ridge 1
In order to make it possible to implant only from the upper part of 0, the contact layer 4 and the upper cladding layer 3 are selectively etched using the insulating film 5 as a mask to form the ridge 10, and then the insulating film 5 is removed. It is necessary to form an insulating film 6 for current constriction so as to cover the surfaces of the upper cladding layer 3 and the contact layer 4, and to remove a region of the insulating film 6 located above the ridge. There was a problem that it became complicated.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide a method of manufacturing a semiconductor laser having a ridge capable of narrowing a current, which can be easily formed. With the goal.

[0012]

A method of manufacturing a semiconductor laser according to the present invention comprises a first conductive type lower cladding layer, an active layer, a second conductive type upper cladding layer, and a second conductive type upper cladding layer on a first conductive type semiconductor substrate. A step of sequentially growing crystals of a conductive type contact layer, a step of forming a stripe-shaped insulating film on the contact layer, and a step of forming a methane gas (CH
₄ ) a step of selectively etching the contact layer and the upper portion of the upper clad layer by dry etching using a gas containing hydrogen gas (H ₂ ) to form a ridge;
A step of forming an electrode metal so as to cover the surface exposed by the etching and an upper part of the contact layer after removing the insulating film; and a step of forming an electrode metal on the back side of the substrate. It is a thing.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a perspective view showing a method for manufacturing a semiconductor laser according to Embodiment 1 of the present invention.
Reference numeral 1 denotes a semiconductor substrate made of n-type GaAs, 1a denotes a lower cladding layer made of n-type AlGaAs, and 2 denotes a plurality of AlGs.
An active layer having a quantum well structure in which aAs layers and GaAs layers are alternately stacked, and an active layer in which AlGaAs layers having different compositions are alternately stacked, or an active layer formed of a single AlGaAs layer may be used. Good. 3 is a p-type AlGaAs
4 is a contact layer made of p-type GaAs, 5 is an insulating film made of SiON, SiO ₂ , SiN, etc., which is used as a mask when ridges are formed by etching, and 7 is an electrode, which is a p-side electrode A metal, 8 is an electrode metal serving as an n-side electrode, 10 is a ridge, and 11 is a hydrogen diffusion region.

Next, a method of manufacturing the semiconductor laser according to the first embodiment will be described. First, 1-2 on the semiconductor substrate 1
Lower clad layer 1a having a thickness of about 0.1 μm, thickness of about 0.1 μm
The active layer 2, the upper cladding layer 3 having a thickness of about 1 to 2 μm, and the contact layer 4 having a thickness of about 0.5 to 3 μm are formed by MOCV.
A crystal is grown by using a D (Metal organic chemical vapor deposition) method or the like (FIG. 1A).

Next, a thickness of about 200 is formed on the contact layer 4.
After forming an insulating film of up to several thousand angstroms, the insulating film is patterned using a photolithography technique or the like, and a stripe having a width approximately equal to the width of a ridge formed in a subsequent process, that is, a width of approximately several μm. Insulating film 5 extending in a shape
Is formed (FIG. 1 (b)).

Subsequently, using the insulating film 5 as a mask, the contact layer 4 and the upper clad are formed by dry etching such as plasma etching or reactive ion etching using methane gas (CH ₄ ) and hydrogen gas (H ₂ ). Layer 3
The upper clad layer 3 has a thickness of 0.1 to 0.5 μm.
The ridge 10 is formed by performing selective etching so as to have a thickness of about m (FIG. 1C). At this time, at the same time as these layers are dry-etched, the hydrogen contained in the dry-etching gas diffuses to a surface exposed by the dry etching to a depth of, for example, about 0.5 μm, so that the hydrogen diffusion region 11 This region is formed to have a high resistance due to diffusion of hydrogen.

Further, the insulating film 5 is formed by dry etching.
Is removed, an electrode metal 7 is formed on the entire upper surface of the substrate 1 so as to cover the upper cladding layer 3 and the contact layer 4, and an electrode metal 8 is further formed on the back surface of the substrate 1, and the laser is formed by cleavage or the like. By forming the cavity end face, a semiconductor laser as shown in FIG. 1D is obtained.

Next, the operation will be described. In the semiconductor laser according to the first embodiment, the region exposed to the outside at the time of dry etching becomes a hydrogen diffusion region 11 due to hydrogen diffusion and has a high resistance. When a current flows, no current flows from the surface of the upper cladding layer 3 where the hydrogen diffusion region 11 is formed and the side surface of the contact layer 4 in the region in contact with the p-side electrode 7, and only from the top of the ridge 10. A current flows, the current is squeezed through the ridge 10 and injected into the active layer 2,
When a current equal to or larger than a certain current value, that is, a current equal to or larger than the threshold current is caused to flow, laser oscillation occurs. Therefore, in this semiconductor laser, similarly to the above-described semiconductor laser having the conventional insulating film 6, the current can be narrowed and injected into the active layer 2, so that a semiconductor laser with high emission efficiency can be obtained. it can.

Here, in the first embodiment, the high-resistance hydrogen diffusion region 11 for narrowing the current can be formed simultaneously with the dry etching for forming the ridge 10. Therefore, a structure for current constriction can be easily formed. Further, a complicated process of forming an insulating film for narrowing a current to a ridge portion, which is required in a conventional method of manufacturing a semiconductor laser, can be eliminated.

As described above, according to the first embodiment, C
Ridge 1 by dry etching using H ₄ and H ₂
0, and then the electrode metal 7 is formed on the upper cladding layer 3 and the contact layer 4, so that the formation of the ridge and the formation of a high-resistance region for current narrowing can be performed simultaneously. In addition to the above, the step of forming an insulating film for narrowing the current is not required, and there is an effect that a semiconductor laser having a ridge capable of narrowing the current can be easily formed.

In the first embodiment, CH
_Although the case where dry etching using ₄ and H ₂ is used has been described, the present invention is also applicable to the case where dry etching using a gas containing CH ₄ and H ₂ is used. In such a case, the same effect as in the first embodiment can be obtained.

In the first embodiment, the case where the n-type semiconductor substrate is used has been described. However, in the present invention, the p-type semiconductor substrate is used and the lower cladding layer is used. The present invention can be applied to the case where the conductivity type is p-type and the conductivity type of the upper cladding layer and the contact layer is n-type. In such a case, the same effect as in the first embodiment can be obtained.

In the first embodiment, a GaAs semiconductor laser having a substrate of GaAs has been described. However, the present invention can be applied to a semiconductor laser using another material. For example, in the semiconductor laser described in the first embodiment, the present invention can be applied to a laser using an AlGaInP layer instead of AlGaAs of the lower cladding layer and the upper cladding layer and using an AlGaInP layer as an active layer, or Using an InP substrate as a substrate, a lower cladding layer, an upper cladding layer,
And an InP layer as a contact layer and In as an active layer.
The present invention can also be applied to an InP-based semiconductor laser using a GaAsP layer. In such a case, the same effect as in the first embodiment can be obtained.

[0024]

As described above, according to the present invention, a first conductive type lower cladding layer, an active layer,
A step of sequentially growing a second conductive type upper cladding layer and a second conductive type contact layer, a step of forming a stripe-shaped insulating film on the contact layer, and a step of forming methane gas (CH _{4) using the} insulating film as a mask. ) And hydrogen gas (H ₂ ) to selectively etch the contact layer and the upper part of the upper cladding layer to form a ridge by dry etching using a gas containing the gas, and to remove the insulating film. Thereafter, a step of forming an electrode metal so as to cover the surface exposed by the etching and the upper part of the contact layer, and a step of forming an electrode metal on the back side of the substrate are provided. The formation of a high-resistance region for current squeezing can be performed at the same time, and the complicated process of forming an insulating film for squeezing current can be eliminated. There is an effect that it is possible to easily form a semiconductor laser with a capacity ridges.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a method for manufacturing a semiconductor laser according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a conventional method for manufacturing a semiconductor laser.

[Explanation of symbols]

Reference Signs List 1 semiconductor substrate, 1a lower cladding layer, 2 active layer, 3
Upper cladding layer, 4 contact layer, 5 insulating film, 6 insulating film, 7, 8 electrode metal, 10 ridge, 11 hydrogen diffusion region.

Claims (1)

[Claims] A first conductive type lower cladding layer, an active layer, a second conductive type upper cladding layer, and a second conductive type contact layer are sequentially grown on a first conductive type semiconductor substrate; Forming a stripe-shaped insulating film thereon; and using the insulating film as a mask, dry etching using a gas containing methane gas (CH ₄ ) and hydrogen gas (H ₂ ) to form the contact layer and the upper clad layer. Forming a ridge by selectively etching the upper portion of the contact layer; and forming an electrode metal so as to cover the surface exposed by the etching and the upper portion of the contact layer after removing the insulating film. A method of manufacturing a semiconductor laser, comprising: a step of forming an electrode metal on a back surface side of the substrate.