JPH054832B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor laser device and a method for manufacturing the same, and more specifically, the present invention relates to a semiconductor laser device and a method for manufacturing the same. The present invention relates to an improved semiconductor laser device and a method for manufacturing the same.

[Conventional technology]

As an example of a conventional semiconductor laser device in which the radiation angle of laser light is narrowed, FIG. 6 shows a schematic configuration of a semiconductor laser device disclosed in, for example, Japanese Patent Application Laid-Open No. 54-6790.

That is, in the conventional configuration shown in FIG. 6, numeral 1 indicates a P-type GaAs crystal substrate, and 2 indicates a P-type
Type Ga _1-x Al _x As cladding layer, 3 is Ga _1-y Al _y As active layer, 4 is N-type Ga _1-x Al _x As cladding layer, 5 is N-type
A Ga _1-z Al _z As light guide layer, 6 an N-type GaAs contact layer, are formed in sequence on the substrate 1, 7 and 8 are electrodes, 9 is a laser beam to be emitted, 10 and 11 is a light intensity distribution, and 12 is a resonator end face.

In this case, 0≦y≦z<x, and for convenience of explanation, P type and N type are interchanged here.

Therefore, in the conventional structure described above, the Ga _1-y Al _y As active layer 3 is usually
P-type Ga _1-x Al _x As gradient layer 2 and N-type Ga _1-x
Since it is formed of a material whose forbidden band width is smaller than that of the Al _x As cladding layer 4, carriers injected from the electrodes 7 and 8 are confined within the Ga _1-y Al _y As active layer 3. The laser beam 9 is efficiently generated, and at the same time, the refractive index of the Ga _1-y Al _y As active layer 3 is P
Type Ga _1-x Al _x As gradient layer 2 and N-type Ga _1-x Al _x
Since it is higher than the As cladding layer 4, Ga _1-y
A light intensity distribution 10 with a strong peak is shown within the Al _y As active layer 3.

On the other hand, in the portion adjacent to the resonator end face 12, in contact with the Ga _1-y Al _y As active layer 3, its forbidden band width is smaller than that of the N-type Ga _1-x Al _x As cladding layer 4. is small and has a low refractive index.
Type Ga _1-z Al _z As light guide layer (0≦y≦z<x)5
is formed, and here, when compared to the part where the Ga _1-y Al _y As active layer 3 is in contact with the N-type Ga _1-x Al _x As cladding layer 4, the light confinement is weaker. , a light intensity distribution 11 with a widening tail is shown.

For this reason, the diameter of the laser beam spot in the thickness direction of the active layer on the cavity end face 12 increases, and the laser beam 9 emitted from the cavity end face 12 does not undergo much diffraction phenomenon, and its radiation angle can be narrowed.

[Problem that the invention seeks to solve]

As described above, in the conventional semiconductor laser device in which the radiation angle of the laser beam is narrowed, in the portion adjacent to the cavity end face 12, the Ga _1-y Al _y As active layer 3 and the N-type layer in contact with the same layer are formed. Since the difference in forbidden band width (y-z) with the Ga _1-z Al _z As optical guide layer 5 is small, carrier confinement within the Ga _1-y Al _y As active layer 3 is insufficient. There are problems such as an increase in threshold current, and when manufacturing it,
Leaving Ga _1-y Al _y As active layer 3, N in contact with the same layer
It is necessary to remove at least a portion of _the Ga _{1 -y} Al _y The upper surface of the As active layer 3 may be exposed to the atmosphere and oxidized, which may adversely affect device characteristics.

This invention was made to solve these conventional problems, and its purpose is to narrow the radiation angle of laser light without increasing the threshold current. Another object of the present invention is to provide a semiconductor laser device of this type and a method for manufacturing the same, in which end face breakage is less likely to occur even at high output.

[Means for solving problems]

In order to achieve the above object, a semiconductor laser device according to the present invention includes a cladding layer of a first conductivity type, an active layer, and a cladding layer of a second conductivity type. , and includes a semiconductor layer having a higher refractive index than that portion in a portion adjacent to at least one resonator end face.

[Effect]

That is, in this invention, carriers and light are sufficiently confined within the active layer by the double heterostructure, and on the other hand, a light guide with a high refractive index is provided on the outer surface of the double heterostructure in a portion adjacent to the cavity end face. Since it has a layer, the confinement of light at the same end face becomes weaker, and the beam spot diameter of the laser light in the direction perpendicular to the active layer becomes larger.
As a result, the optical density is reduced, optical end face destruction can be prevented, and the diffraction phenomenon of laser light emitted from this end face is suppressed, making it possible to narrow the radiation angle.

〔Example〕

Hereinafter, various embodiments of a semiconductor laser device and a method for manufacturing the same according to the present invention will be described in detail with reference to FIGS. 1 to 5.

In each of the embodiments shown in FIGS. 1 to 5, the same reference numerals as in the conventional example shown in FIG. 6 represent the same or corresponding parts.

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

In this first embodiment device, in the conventional configuration described above, the N-type Ga _1-x Al _x As cladding layer 4 and the N-type
An N-type Ga _1-x Al _x As semiconductor layer 13 is formed between the GaAs contact layers 6, and this semiconductor layer 13
N for the portion adjacent to the resonator end face 12 within
A Ga _1-z Al _z As light guide layer 5 is formed. Then, this N-type Ga _1-x Al _x As semiconductor layer 1
Regarding the Al composition ratio x in 3, the P type Ga _1-x Al _x As cladding layer 2 and the N type
The Ga _1-x Al _x As cladding layer 4 is made to be the same as that of the Ga 1-x Al x As cladding layer 4.

Therefore, in the case of the device configuration according to the first embodiment, the P-type Ga _1-x Al _x As cladding layer 2 and the N-type
The Ga _1-x Al _x As cladding layer 4 has an Al composition ratio of 0.
Relationship of ≦y<x, e.g. x=0.3~0.6, y=0~
0.2, forming a double heterostructure. Therefore, when carriers are injected from the electrodes 7 and 8, the carriers are confined within the Ga _1-y Al _y As active layer 3, and the carriers are Through recombination, the target laser light is stimulated to be emitted.

At this time, when the N-type Ga _1-x Al _x As cladding layer 4 is formed as thin as, for example, about 0.01 to 1.0 μm, this N-type Ga _1-x Al _x As cladding layer 4
In the part where the active layer 3 is in contact with the N-type Ga _1-x Al _x As semiconductor layer 13, the Ga _1-y Al _y As active layer 3 is sandwiched between sufficiently thick cladding layers from both sides. The laser light takes the form of a light intensity distribution 10 that is effectively confined within the Ga _1-y Al _y As active layer 3, and this N-type Ga _1-x Al _x As cladding layer 4 is, for example, z = N of 0 to 0.6 (y≦z<x)
In the part in contact with the type Ga _1-z Al _z As light guide layer 5, the laser light in the Ga _1-y Al _y As active layer 3 is
The light leaks into the N-type Ga _1-z Al _z As light guide layer 5 and takes the form of a light intensity distribution 11 .

That is, as the laser beam spot diameter in the direction perpendicular to the active layer 3 at the cavity end face 12 increases equivalently in this way, the optical density at the same end face decreases, even during high-power operation. ,
Since it is difficult to cause optical end face destruction and to be less susceptible to diffraction phenomena, the radiation angle of the laser beam 9 emitted from the resonator end face 12 can be narrowed. Since it is formed only in the portion adjacent to the end face 12 of the device, it is possible to easily prevent the vertical transverse mode from becoming a higher order mode due to the light guide layer 5 in the device as a whole.

Furthermore, in the device configuration according to the first embodiment, the N-type Ga _1-z Al _z As optical guide layer 5 is formed only in the portion adjacent to the cavity end face 12, but as shown in FIG. As shown in the second embodiment, this N-type Ga _1-z Al _z As light guide layer 5 is
A state in which the thickness is thin over the entire surface between the Ga _1-x Al _x As cladding layer 4 and the N-type Ga _1-x Al _x As semiconductor layer 13, and the thickness is thick in the portion adjacent to the resonator end face 12. Similar effects and effects can be obtained even if formed in the form of

Furthermore, FIG. 3 shows the device configuration according to the third embodiment, in which reference numeral 1a indicates an N-type GaAs crystal substrate, 6a indicates a P-type GaAs contact layer, and 14 indicates an etched groove on the end surface. As in the configuration of this third embodiment, when viewed from the Ga _1-y Al _y As active layer 3 side, the N-type Ga _1-z Al _z As optical guide layer 5 is placed on the N-type GaAs crystal substrate 1a side. Even if it is formed, similar actions and effects can be obtained.

Next, FIGS. 4A to 4F are perspective views sequentially showing the manufacturing process of the semiconductor laser device according to the first embodiment.

That is, first, after forming an N-type GaAs current blocking layer 15 on a P-type GaAs crystal substrate 1 (see a in the figure), this N-type GaAs current blocking layer 1 is
A selected portion of the groove 5 is removed by etching in a stripe pattern to form a stripe groove 16 (FIG. 1b).

Then, a P-type Ga _1-x Al _x As cladding layer 2, a Ga _1-y Al _y As active layer 3, an N-type Ga _1-x Al _x As cladding layer 4, and an N-type Ga _1-z Al _z As light guide layer 5
are sequentially formed (c in the same figure). However, in this case,
0≦y≦z<x.

The N-type Ga _1-z Al _z As optical guide layer 5 is selectively and partially left in the direction perpendicular to the stripe groove 16, and the remaining part is formed into the N-type Ga 1-z Al z As light guide layer 5. Ga _1-x Al _x As cladding layer 4
The light guide layer removal groove 17 is formed by etching until it is exposed (d in the same figure). At this time, the N-type Ga _1-z Al _z As light guide layer 5 has an Al composition ratio of N-type Ga _1-x Al _x As cladding layers 4 and z
Because of the relationship <x, only the required portions of the light guide layer can be selectively etched away with good control using, for example, an ammonia-hydrogen peroxide-based etching solution.

Subsequently, an N-type Ga _1-x Al _x As semiconductor layer 13 and an N-type GaAs contact layer 6 are sequentially formed on these, and then electrodes 7 and 8 are formed respectively (e in the same figure). Finally, the semiconductor laser device is cleaved along the cleavage line 18 and separated into chips along the chip separation line 19 to obtain the desired semiconductor laser device, which corresponds to the first embodiment (f in the same figure). .

FIGS. 5a to 5e are perspective views sequentially showing the manufacturing process of the semiconductor laser device according to the third embodiment.

That is, first, after forming stripe-shaped etching grooves 14 on the end face of the substrate on the N-type GaAs crystal substrate 1a (see a in the figure), the N-type Ga _1-x Al _x As semiconductor layer 13 is etched in the same grooves. The N-type Ga _1-z Al _{z As optical guide layer 5 is formed so that the corresponding portion of the groove 14 is not flat, and then the N-type Ga 1-z Al z} As optical guide layer 5 is formed so that the corresponding portion of the groove 14 is flat. Ga _1-x Al _x As clad layer 4, Ga _1-y Al _y As active layer 2, P-type Ga _1-x Al _x As clad layer 2, and N-type GaAs current blocking layer 1
5 are formed one after another (see figure b).

Next, stripe-like etching is performed on the N-type GaAs current blocking layer 15 in a direction perpendicular to the substrate edge etching groove 14, thereby forming the P-type Ga _1-x Al _x As cladding layer. 2
A part of the active stripe groove 16 is exposed to form an active stripe groove 16 (FIG. 3(c)).

Then, on top of that, a P-type Ga _1-x Al _x As semiconductor layer 2 is formed.
0, a P-type contact layer 6a and electrodes 7 and 8 are formed thereon (d in the same figure), and finally, the chip is cleaved along the cleavage line 18 and the chip separation line 19 is formed.
By separating the chips along the lines, the desired semiconductor laser device corresponding to the third embodiment is obtained (see e in the same figure).

However, in the semiconductor laser devices obtained by the methods of each of these embodiments, the optical guide layer is formed in a portion adjacent to the resonator end facet on one or both sides, but the same operation and effect are obtained in either case. is obtained. In addition, here, the optical guide layer is formed over the entire area in the direction parallel to the PN junction in the part adjacent to the cavity end face, but it may also be formed only in the vicinity of the active stripe groove. Of course, in addition to the configurations of these embodiments, the following can be applied to all semiconductor laser devices with or without a stripe structure.

Further, regarding Example 1, the conductivity type of the light guide layer is not particularly important. Furthermore, in the above embodiment, for simplicity, the Al composition ratios of the P-type cladding layer 2, the N-type cladding layer 4, and the P-type semiconductor layer 13 were all made the same, but even if they are not the same, the same effect can be obtained. It will be done.

〔Effect of the invention〕

As detailed above, according to the present invention, the first
In a semiconductor laser device having a cladding layer of a conductivity type, an active layer, and a cladding layer of a second conductivity type, a portion on the outer surface of the cladding layer and adjacent to at least one cavity end face has a higher refraction than that portion. By providing a semiconductor layer with a high ratio, the light emission angle is narrow without increasing the threshold current or converting the vertical transverse mode into a higher-order mode, and even during high-power operation, edge destruction occurs. This makes it possible to extremely easily obtain a semiconductor laser device that is difficult to manufacture.

[Brief explanation of the drawing]

1, 2, and 3 are longitudinal sectional side views showing the schematic configurations of the first, second, and third embodiments of the semiconductor laser device according to the present invention, and FIGS. 4a to 4 f and FIGS. 5a to 5e are perspective views showing the manufacturing method of the first and third embodiment configurations in the order of steps, and FIG. 6 shows a general configuration of the same device according to the conventional example. FIG. 1...P-type GaAs crystal substrate, 1a...N-type
GaAs crystal substrate. 2...P-type Ga _1-x Al _x As cladding layer, 3... Ga _1-y Al _y As active layer, 4... N-type Ga _1-x
Al _x As cladding layer, 5... N-type Ga _1-z Al _z As optical guide layer, 13... P-type Ga _1-x Al _x As semiconductor layer, 2
0...N-type Ga _1-x Al _x As semiconductor layer. 12...Resonator end face, 14...Substrate end face etching groove, 16
...Active stripe groove, 17... Light guide layer removal groove.

Claims (1)

[Scope of Claims] 1. In a semiconductor laser device having a cladding layer of a first conductivity type, an active layer, and a cladding layer of a second conductivity type, on the outer surface of the cladding layer and adjacent to at least one cavity end face. 1. A semiconductor laser device comprising a semiconductor layer having a refractive index higher than that of the portion. 2. A step of sequentially forming a first conductivity type gradient layer, an active layer, a second conductivity type cladding layer, and a light guide layer on a crystal substrate, and forming a resonator end face of at least one of the light guide layers. After removing the portion other than the portion adjacent to the light guide layer by selective etching, a second layer having a refractive index lower than that of the light guide layer is added to the removed portion.
A method for manufacturing a semiconductor laser device, comprising the step of forming a conductive type semiconductor layer. 3. A step of digging an etching groove in a portion of the crystal substrate adjacent to at least one resonator end face, and a step of forming a semiconductor layer of the first conductivity type on the substrate without losing the shape of the etching groove. , forming an optical guide layer having a higher refractive index than the same layer by filling the etching groove on the semiconductor layer of the first conductivity type, and forming a cladding layer of the first conductivity type and an active layer on the optical guide layer. 1. A method of manufacturing a semiconductor laser device, comprising the steps of sequentially forming a cladding layer of a second conductivity type and a second conductivity type cladding layer.