JPS63293989A - Semiconductor laser element and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a semiconductor laser element having small astigmatism by forming the principal section of a resonator in the structure of longitudinal multimode oscillation while at least one end section of the resonator is shaped index guide structure for longitudinal single-mode oscillation. CONSTITUTION:A central principal section extending over 60%-80% of a resonator 3 is formed in a narrow width resonator section 4, width (c) of which is as narrow as 3-5 mum. Both end sections of the resonator 3 are shaped in a wide resonator sections 5, width (b) of which is, for example, 5-10 mum. Since the resonator 3 is wide in the wide resonator section 5, the edge faces of the resonator 3 are not likely to be deteriorated and an electrostatic breakdown level is elevated, thus allowing the increase of an output. Since the thickness of P-type clad layers in the wide resonator sections 5 is shaped thinly, a longitudinal mode is changed into a single mode, and index guide structure is formed, thus reducing astigmatism.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser device, and particularly to a semiconductor laser device with low noise and astigmatism and high output, and a method for manufacturing the same.

[Conventional technology]

Semiconductor lasers are used in the communication field, mainly in optical fiber communications, and in the information terminal field, mainly in optical disk files, digital audio disks, video disks, laser beam printers, and the like.

On the other hand, in recent years, there has been a strong demand for higher output semiconductor lasers. For example, "Nikkei Electronics J, November 19, 1984 issue, P187-P2O6, published by Nikkei McGraw-Hill.
An explanation was published in ``High-power semiconductor lasers that meet the demands of optical discs and push the limits of performance.'' This document describes something similar.

Semiconductor lasers are also being researched and developed in different directions as electronic components. Increasing output power is one direction. Other trends include shorter wavelengths, lower prices, and higher reliability.

Furthermore, depending on the application, mode stability and noise resistance may be important.

Furthermore, in the field of write-once optical discs and erasable/rewritable optical discs, there is the strongest demand for high-power semiconductor lasers as recording light sources. In the field of optical disks, there are many advantages to increasing the output of a semiconductor laser, but simply increasing the output does not make it usable. The transverse mode of a semiconductor laser is assumed to be basic and single. This is because we want to achieve highly accurate focusing without complicating the optical system. Naturally, the far-field pattern of the light beam is in the direction perpendicular to the semiconductor laser junction surface,
A clean Gaussian distribution is good in both the horizontal direction.

The ellipticity of the cross-sectional shape is required to be about 1:2 to 2.5. Astigmatism is 2 to 3 μm or less.

[Problem that the invention seeks to solve]

As mentioned above, in the field of optical disks and the like, there is a demand for semiconductor lasers with higher output, lower noise, and lower astigmatism.

In order to reduce noise in semiconductor lasers, efforts are being made to make them vertically multi-mode. However, although this vertical multi-mode structure is an effective technology, problems such as an increase in astigmatism and a decrease in the level of electrostatic damage occur due to the structure of the longitudinal multi-mode structure.
It turned out that there were many practical problems.

An object of the present invention is to provide a semiconductor laser element with small astigmatism.

Another object of the present invention is to provide a semiconductor laser device that can achieve low noise.

Another object of the present invention is to provide a high output semiconductor laser device.

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Means for solving problems]

A brief overview of typical inventions disclosed in this application is as follows.

That is, the semiconductor laser device of the present invention is made of p-type GaAs
The structure has an n-type GaAs layer on the main surface of the substrate, and this n-type GaAs layer is partially etched to have a groove whose bottom reaches the surface layer of the underlying substrate. Further, a p-type cladding layer, an active layer, an n-type cladding layer, and a cap layer are sequentially provided on the main surface side of the substrate. Further, the groove width at the center portion, which is 60% to 80% of the length of the groove, is 3 μm.
5 μm, and the thickness of the p-type cladding layer in this portion is 0.3 μm to 0.5 μm, so that a laser beam whose longitudinal mode is multi-mode is emitted.

Further, the groove width at both end portions of the groove is as wide as 5 μm to 10 μm, and the thickness of the p-type cladding layer in this portion is 0.
．． It is approximately 2 μm and is of a refractive index guide type.

[Effect]

According to the above means, the semiconductor laser device of the present invention is
Since the central main portion, which occupies 60% to 80% of the length of the resonator, has a multi-mode longitudinal mode, the structure is strong against return optical noise, and low noise can be achieved. Furthermore, since the groove width is widened at both end portions of the resonator, deterioration of the end faces of the resonator is less likely to occur, and high output can be achieved. Furthermore, since both end portions of the resonator have a refractive index guide structure, astigmatism is reduced to 5 μm or less.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing an outline of a semiconductor laser device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line ■ to ■ in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line mm in FIG. FIG. 4 is a perspective view showing a part of a wafer in one step of manufacturing the semiconductor laser device of the present invention, and FIG. 5 is a cross-sectional view of the wafer on which a multilayer growth layer is formed.

The semiconductor laser device of this example is suitable for use in compact discs, and its structure is C3P (cha
It has an internal current confinement structure as well as an internal current confinement structure.

As shown in FIG. 1, one of the features of the semiconductor laser device 1 of this embodiment is that the resonator 3 that emits the laser beam 2 is wide at both ends thereof. . That is, the main central portion of the resonator 3, which covers 60% to 80%, is a narrow resonator portion 4 whose width C is as narrow as 3 μm to 5 μm. This will be explained in detail later, but this is because the thickness of the p-type cladding layer corresponding to the narrow resonator portion 4 is thicker, for example, 0.3 to 0.5 μm or more. The mode is set to emit light.

Moreover, the width of both ends of the resonator 3 is 5 μm-JO
The resonator portion 5 has a wide width of μm. In this wide resonator portion 5, since the width of the resonator 3 is wide, the end face of the resonator 3 is difficult to deteriorate, the electrostatic damage level is improved, and high output is possible. In addition, this wide resonator portion 5
Since the p-type cladding layer is formed thin, the longitudinal mode becomes a single mode and a refractive index guide structure is formed, thereby reducing astigmatism. In FIG. 2, a cross section of the semiconductor laser device 1 is shown in the narrow resonator portion 4, and the third
In the figure, a cross section of the semiconductor laser element l of the wide resonator portion 5 is shown.

Further, the length A of the narrow resonator portion 4 is 60% to 80% of the total length of the resonator 3. Therefore, the length a of the wide resonator portion 5 is 10% to 20% of the total length of the resonator 3.
It will be about %.

Next, a semiconductor laser element l having such a structure will be explained.

As shown in FIGS. 2 and 3, the semiconductor laser device 1 has a substrate 6 made of p-type GaAS and having a thickness of 100 μm. Further, on the main surface of this substrate 6, a current confinement layer 7 made of n-type GaAs and having a thickness of 0.8 μm is provided. The current confinement layer 7 is divided at its center by a striped groove 8. This groove 8 is connected to the lower substrate 6.
It is formed so that it can penetrate as far as the As described above, this groove 8 has a narrow resonator portion 4 having a narrow groove width at the center of the resonator 3, and a wide resonator portion 5 having a wide groove width at both end portions of the resonator 3.

On the other hand, on the current confinement layer 7 and the exposed substrate 6,
The p-type cladding layer 9 made of p-type GaAlAs and the p-type cladding layer 9 made of p-type GaAlAs,
G with a thickness of 0.07 μm formed on the shaped cladding rM9
An active layer 10 made of aAs, an n-type cladding layer 11 made of n-type GaAfLAs with a thickness of 2 μm formed on the top surface of this active layer 10, and a thickness formed on the top surface of this n-type cladding layer 11. A multi-layered growth layer is formed including a cap 1112 made of 1 μm n-type GaAs.

On the other hand, the thickness of the p-type cladding layer 9 is different between the narrow resonator portion 4 and the wide resonator portion 5 of the resonator 3. That is, p of the narrow resonator portion 4
The thickness f of the shaped cladding N9 is 0.3 μm so that the longitudinal mode of the laser beam becomes multi-mode in the narrow resonator portion 4.
The thickness is approximately 0.5 μm. That is, the thickness of the p-type cladding layer 9 of this narrow resonator portion 4 is 0.3 μm.
As the degree increases, the longitudinal mode becomes multimode.

Further, the thickness g of the p-type cladding layer 9 of the wide resonator portion 5 is as thin as 0.2 μm, and the longitudinal mode is a single mode.

Further, a cathode electrode 13 is provided on the cap layer 12, and an anode electrode 14 is provided on the back surface of the substrate 6. In this semiconductor laser device 1, the current confinement N7 constricts the region through which the current flows.

Next, a method for manufacturing such a semiconductor laser device 1 will be explained.

In manufacturing the semiconductor laser device 1, first the wafer 1 is
5 will be prepared. The wafer 15 in this case has a thickness of 350 mm.
It is composed of a p-type GaAs substrate 6 of μm. Incidentally, on the main surface of this wafer 15, multi-layered growth layers and the like are sequentially formed thereafter, but the wafer, including each of these layers, is referred to as a wafer until it is made into chips.

Next, a current confinement layer 7 made of n-type GaAs and having a thickness of 0.8 μm is formed on the main surface of the wafer 15 by MOCVD. This current confinement layer 7 is partially etched into stripes as shown in FIG. During this etching, the stripe portion facing the edge of the chip region 16 shown by the solid line is etched to a wider width. As a result, the narrow resonator portion 4 and the wide resonator portion 5 as described above are formed.

Next, as shown in FIG. 5, p-type GaAlA is grown on the main surface of the wafer 15 by liquid layer epitaxial growth.
p-type cladding layer 9 consisting of s. Ga with a thickness of 0.07μm
Active layer 10 made of As, n-type G with a thickness of lpm
a A fL N-type cladding layer 11 consisting of A-5. A cap layer 12 made of n-type GaAs having a thickness of 1 μm is successively formed. At this time, in the case where the thickness of the p-type cladding layer 9 on the narrow resonator portion 4 of the resonator 3 is set to about 0.35 μm, the longitudinal mode is made into a multi-mode in consideration with the width of the groove 8. , the thickness of the p-type cladding N9 of the wide resonator portion 5 is as thin as, for example, 0.2 μm because the width of the resonator 3 of the wide resonator portion 5 is wider than that of the narrow resonator portion 4. Become. As a result, in the wide resonator portion 5, the longitudinal mode of the laser beam becomes a single mode, and the astigmatism becomes small.

Next, a cathode electrode 13 is formed on the main surface of the wafer 15. This cathode electrode 13 has a multilayer structure with a thickness of 1 μm, for example, in which the bottom layer is AuGeN+, the middle layer is Cr, and the upper layer is Au.

Next, the back surface of the wafer 15, ie, the back surface of the substrate 6, is etched to a thickness of approximately 100 μm. Thereafter, an anode electrode 14 is formed on the back surface of the wafer 15. This anode electrode [14] has a lower layer of Cr and an upper layer of Au, and has a thickness of about 1 μm.

Next, the wafer 15 is divided vertically and horizontally.
A semiconductor laser device 1 as shown in the figure is obtained.

According to such an embodiment, the following effects can be obtained.

(1) The semiconductor laser device of the present invention has 60% or more of the resonator.
Since the longitudinal mode becomes multi-mode in the main part, which accounts for 80%, the semiconductor laser element becomes strong against returned light, and the effect of achieving low noise can be obtained.

(2) In the semiconductor laser device of the present invention, since the end portions of the resonator are wide, deterioration at the end faces of the resonator is less likely to occur, so that high output can be achieved.

(3) In the semiconductor laser device of the present invention, since the end portion of the resonator is wide and the p-type cladding layer in this portion is thin, the end portion of the resonator is of a refractive index guided type. The effect is that the astigmatism is reduced to, for example, 5 μm or less.

(4) According to the above (1) to (3), according to the present invention, a synergistic effect can be obtained in that it is possible to provide a high output semiconductor laser device with low noise and astigmatism.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. Nor. For example, in the semiconductor laser device described above, the active layer has a flat structure, but even if it has a curved structure, the same effects as in the embodiment described above can be obtained.

FIG. 6 shows a semiconductor laser device 1 according to another embodiment of the present invention.
It is. In this example, only one end of the resonator 3, i.e.
A wide resonator portion 5 is provided on the output side. This makes it possible to reduce astigmatism and noise while increasing output.

In the above description, the invention made by the present inventor is mainly applied to the technology for manufacturing semiconductor laser elements for compact discs, which is the background field of application, but the invention is not limited thereto.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

The semiconductor laser device of the present invention has 60% to 80% of the resonator.
The central main part, which occupies the length, has a multi-mode longitudinal mode, so it has a structure that is strong against return optical noise and can achieve low noise. End face deterioration is less likely to occur and high output can be achieved, and since both ends of the resonator have a refractive index guide structure, astigmatism is reduced to less than 5 μm.
Improves connectivity with optical system.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an outline of a semiconductor laser device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line nn in FIG. 1, and FIG.
4 is a perspective view showing a part of a wafer in one step of manufacturing the semiconductor laser device of the present invention, and FIG. 5 is the same (multilayer growth layer is formed). 6 is a schematic plan view showing a semiconductor laser device according to another embodiment of the present invention. 1... Semiconductor laser device, 2... Laser light, 3...
- Resonator, 4... Narrow resonator part, 5... Wide resonator part, 6... Substrate, 7... Current confinement layer, 8...
Groove, 9...p-type cladding layer, 10...active layer, 11
... n-type cladding layer, 12... cap layer, 13.
...Cathode electrode, 14...Anode electrode, 15...
・Wafer, 1\"1., N"""'1 --'El-' 3vA Fig. 5

Claims (1)

[Claims] 1. The main part of the resonator has a structure that oscillates in a longitudinal multi-mode, and at least one end portion of the resonator has a refractive index guide structure that oscillates in a single longitudinal mode. semiconductor laser device. 2. The width of both end portions of the resonator is wider than the groove width of the central portion of the resonator, and the thickness of the p-type cladding layer on the groove is thinner than that of the central portion. A semiconductor laser device according to claim 1. 3. A step of forming an n-type GaAs layer on the main surface of the p-type GaAs substrate, a step of partially etching this n-type GaAs layer to form a groove reaching the surface layer of the underlying substrate, and a step of forming an n-type GaAs layer on the main surface of the substrate. A method for manufacturing a semiconductor laser device, comprising the step of sequentially epitaxially growing a p-type cladding layer, an active layer, an n-type cladding layer, and a cap layer on the surface side,
The main part including the center of the groove has a narrow groove width, and at least one end part of the groove has a wide groove width, and the thickness of the p-type cladding layer in the narrow groove part is equal to that of the narrow groove part. The p-type cladding layer is thick so that the resonator oscillates in longitudinal multi-mode, and the thickness of the p-type cladding layer in the wide groove part is thin so that the resonator oscillates in a longitudinal single mode in the wide groove part. A method for manufacturing a semiconductor laser device.