JPS62269383A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain a reproducible semiconductor leser so that the laser emits its highly efficient and uniform beams in the different directions to one another by holding a super lattice as a part of respective structure elements and employing a semiconductor laser that is prepared by a MBE or MOCVD system. CONSTITUTION:Four laminations comprising N-type GaAs 22, N-type Al0.4Ga0.6 As 23, non-doping GaAs, and Al0.2Ga0.8As are performed repeatedly in sequence on an N-type GaAs substrate 21 and finally an active area 24 is formed by laminating GaAs. In addition, P-type Al0.4Ga0.6As 25 are GaAs 26 are formed by a molecular beam epitaxy system. After etching up to just this side of the active layer 24 in order to limit an area applied by an electric current, a nitriding silicon film 27 is formed by a plasma CVD system and only the top part of ridge is processed by etching, resulting in the formation of Cr-Au ohmic electrode and also, resulting in the formation of five independent electrodes 11d-15d after separating them by etching. Then, an Au-Ge electrode is vapor deposited as an ohmic electrode 29 for N type to cleave resonance faces 16 and 17 after performing a heat treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a semiconductor laser device in which a plurality of semiconductor lasers are monolithically formed.

[Prior art]

Conventional 1 For example, as disclosed in Japanese Unexamined Patent Publication No. 59-126, when designing an optical scanning device using a plurality of semiconductor lasers or light emitting diodes (LEDs), the light emitted from the light emitting body is The light source was designed so that the emission directions of the two intersected each other at one point PO, so that a plurality of scanning spots could be scanned on a surface to be scanned (not shown) while maintaining a good image formation state.

FIG. 3 shows a typical conventional example, and is a diagram of the optical system between the light source and the deflector, viewed from a direction perpendicular to the deflection scanning plane. 31a and 31b are semiconductor lasers, and each laser is arranged on the mount 32 so that its light beam generating surface is parallel to the end surface of the mount 32. Semiconductor laser 31a.

The end faces 32a, 3 of the mount 32 where the mount 31b is provided
2b is set as if the central rays ha and hb of the diverging light beams from the respective lasers 31a and 31b had passed through the same point P. In other words, semiconductor lasers (31a, 31
If the normal lines are drawn to the end faces 32a and 32b at the position where b) is provided.

The end faces 32a and 32 are arranged so that each normal passes through Po.
b is set. Furthermore, when viewed from a direction parallel to the deflection scanning plane, the central light 111h a of each semiconductor laser
, h b The position of the semiconductor laser provided on the mount 32 is set so that the position where it passes through the PO point is slightly displaced in a direction perpendicular to the deflection scanning plane. Above P
Point O and a point P in a predetermined vicinity of the deflection reflection surface 33 of the deflector are maintained in an optically conjugate relationship by the imaging lens 34.

In this way, in order to arrange multiple semiconductor light emitting devices (for example, semiconductor lasers) so that their respective light emission directions are different, it is necessary to align the mounts as shown in the example above and create a hybrid. needed to be configured. For convenience, the term "array laser" will be used below to refer to a plurality of semiconductor light emitting elements, but in principle it also applies to light emitters such as LED arrays.

Furthermore, when using a monolithically formed array laser, it is necessary to install some kind of optical system in front of the array laser. In an example disclosed in Japanese Patent Laid-Open No. 58-211735, a prism is placed in front of an array laser.

This is shown in FIG.

FIG. 4 shows a cross section of a prism when a semiconductor array laser has five light emitting parts.

41 is five light emitting parts (41a, 41b, 41c).

41d, 41e),
42 is a prism 6 The central light of the luminous flux from the light emitting part 41a &9h a is refracted by the inclined surface 42a, as if P
It is bent as if it had passed through O. Same <41
The central ray hb from b is caused by the inclined surface 42b, the central ray hd from 41d is caused by the inclined surface 42d, and the central ray he from 41e is caused by the inclined surface 42a, as if P
It is bent as if it had passed through O. Note that the central ray he from 41c passes through the plane 42c perpendicularly,
PO exists on an extension of this central ray he. In this way, an inclined plane with a defined tilt angle is provided corresponding to each light emitting part, and the direction of the central ray of each luminous flux after passing through the prism 42 is controlled as if it were emitted from the PO. ing. As described above, this PO is kept conjugate with a desired position P (not shown) near the deflection/reflection surface via the optical system.

Problems in this case include the precision and method of microfabrication of the prism 42, the alignment and bonding method between the prism 42 and the seven-ray laser 41, and this becomes more difficult as the pitch of the array laser becomes smaller. In fact, it is almost impossible to use less than 1100 IL.

On the other hand, FIG. 5 shows an attempt to have a similar effect with an optical system, that is, a relay optical system 53, with array lasers 51a, 5
This is an example in which a relay optical system 53 is interposed between a collimator lens 52 and a cylindrical lens 55 that collimate and image the light emitted from 1b, and an image is formed on a polygon surface 54, and the image is scanned in a good image formation state. The image is formed on a surface (not shown). The problem in this case is the optical path length, and the relay system itself becomes about 20 cm longer.

- On the other hand, in order to solve the above-mentioned problems, the present applicant has proposed in Japanese Patent Application No. 59-240418 and Japanese Patent Application No. 60-424 that a plurality of semiconductor lasers are formed monolithically and each A semiconductor device in which semiconductor lasers emit light in different directions has already been proposed.

[Summary of the Invention] An object of the present invention is to provide a semiconductor laser device that can be easily manufactured and that can be combined with a lens etc. to construct an optical system with a short optical path length. There are things that can further improve the performance of devices that have already been proposed.

The above object of the present invention is to provide a semiconductor laser device in which a plurality of semiconductor lasers are monolithically formed, each of the semiconductor lasers having a superlattice structure in a part thereof, and
This is achieved by forming these semiconductor lasers by molecular beam epitaxy or metal oxide vapor phase epitaxy so that they emit light in different directions.

Note that the expression "the directions of light emitted from each laser are different" used in the following description does not mean that there are no sets of lasers that emit light in the same direction; This means that there are more than one set.

A problem with integrating a large number of semiconductor lasers at high density is that the emission efficiency decreases due to heat generation and temperature rise associated with carrier injection for oscillation, and it is no longer possible to obtain a constant optical output with a constant injection current. It disappears.

This is serious when used as a light source for an optical recording device such as a semiconductor laser, leading to recording errors and deterioration of recording quality.

The specific solution presented in the present invention is to reduce the above-mentioned reduction in luminous efficiency by applying molecular beam epitaxy (MBE) or metal oxide vapor phase epitaxy (MOO) to the structure of a semiconductor laser.
This is achieved by improving the characteristics by employing a superlattice structure created by the CVD method as part of the growth layer.

That is, as described in the following embodiments, by employing the above structure, (1) the injection current required for light emission is reduced, the amount of heat generated to obtain the same level of light output is reduced, and the operating temperature is lowered.

(2) Good temperature characteristics, with little fluctuation in light output even during high-temperature operation.

(3) Variations in performance between adjacent elements are small, and homogeneous output can be obtained from a plurality of output ends.

Due to the combined effect of (1) to (3) above, good light emission characteristics were achieved regardless of the light emission history even in the obliquely emitting array laser that is highly integrated as in the present invention.

〔Example〕

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

In FIG. 1, which shows an embodiment of the present invention, 11 to 15 indicate individual semiconductor lasers, and lla to 15a correspond to current injection regions, that is, light emission regions in each of the semiconductor lasers 11 to 15. Then, the extension m of this injection region 11a-15a
(Hereinafter, referred to as the resonance direction.) The angles formed between llb-15b and the normal line 18 erected to the resonance surfaces 16 and 17 are each φa.

φb, φC1φd, and φe.

Note that the resonant planes 16 and 17 are parallel because the cleavage planes of a crystal (e.g., GaAs) used as a substrate are normally used, but in cases where there is a possibility that the degree of parallelism will be slightly impaired, such as during dry etching. In this case, the resonance surface 16 on the laser emission front side is considered as a reference.

When the light resonated at the resonant surfaces 16 and 17 is emitted from the resonant surface 16 as a laser beam, it is bent according to Snell's law. In the figure, 1ie-15c indicates the light emission direction.

Here, if the angle between an arbitrary light emission direction and the normal line 18, that is, the emission angle, is θ, then n/no=sinθ/
The relationship s i nφ holds true. For example, considering the case where the laser beam is emitted from a GaAs crystal, n (the refractive index of the crystal) is approximately 3.5 and no (the refractive index of the air) is approximately 1, so if φ is chosen to be one degree, the laser beam will be The light is emitted at an angle of about 3.5 degrees with respect to the line 18.

In the embodiment shown in FIG. 1, φa, φb, φC2φd, φ
e is +1.0 degree and +0.5 degree, respectively.

By setting them to 0.0 degrees, -0.5 degrees, and -1.0 degrees, the output angles 6&, θb, θC2θd, and θe are +
3.5 degrees, +1.75 degrees, 0.0 degrees, -1.75 degrees.

We were able to create an array laser with an angle of -3.5 degrees.

FIG. 2 is a sectional view taken along line 8-A' in FIG. 1. The manufacturing process will be described in detail below using this diagram.

First, n-type GaAs 22 is sequentially formed as a buffer layer on an n-type GaAs substrate zl. m, n as cladding layer
type AMo, 4Gao, 2pm of 6As, 100 undoped GaAs as active layer, A jl O, 2G a
6. Repeat B A S 30 people 4 times and finally Ga
As1OO people were stacked. Active region 2 with multiple quantum well structure
4 as the zero-order cladding, type AJL□, 4G
a□, 6As 25 1.5 pm, G as gap layer
0.5 gm of aAs26 was formed by molecular beam epitaxy.

Next, in order to limit the current injection region, as shown in FIG. 2, the active layer 24 is etched to about 0.4 μm in front of L, and then a silicon nitride film 27 is formed by plasma CVD method, and only the top of the ridge is etched. This was used as the injection area.

The injection area width is 3gm and each of the 5 tree stripes is 0gm.
．． It is formed at an angle of 5 degrees.

Next, a Cr--Au ohmic electrode was formed as an upper electrode and separated by etching to form five independent electrodes 1id-15d.

In addition, the GaAs substrate 21 was scraped to a thickness of 1100p by lapping, and then A
A u-Ge electrode was deposited.

After a subsequent heat treatment for diffusion, the resonant surfaces 16 and 17 were separated as shown in FIG. 19 surfaces were separated using a scribe.

Note that the pitch of each laser is l1 at the resonant surface 16.
It is 00JL. On the other hand, each of the Jill-15d samples was taken out independently by wire bonding (not shown). Here, the cavity length (distance between resonance surfaces 16 and 17)
is 300 pm.

As a result, it was possible to form a monolithic structure with five laser beams each having a different light emission direction by 1.75 degrees within the same plane.

The MBE method and MOCVD method are suitable for uniformly and reproducibly distributing an ultra-thin film structure during crystal growth, and semiconductor lasers with a superlattice structure created by these methods are capable of oblique emission. I found out which car is suitable for creating multiple lasers.

As examples having other superlattice structures, among the previous embodiments,
Growth around the active layer is performed using n-type Alo, 4Ga□, 6A
s to 27tm, followed by n-type Ai0.2Ga□, BAs
2000 people, non-doped GaAs 80 people, p-type Al
to, 2Gao, 2000 aAs, p-type An
When a single quantum well structure in which O, 4G a O, and S A S was 1.5 lm was adopted, the luminous efficiency was also improved, and the same effect as described in Section 2 could be obtained.

In addition, GradedInde in which the composition change on both sides of 80 non-doped GaAs was gradually changed from 0.2 to 0.4.
Similarly good results were obtained with the x-type structure.

In addition, in these structures, a GaAs superlattice of about 50 layers is formed in the middle of the n-type A 0.4Ga0.6As cladding layer.
Even better results were obtained in a structure in which several layers were arranged every 0 people.

It goes without saying that the same effect can be obtained even if the p-type and n-type in the examples are replaced with each other.

In the semiconductor device according to the present invention, array lasers with different light emission directions are created using cleavage planes, but the present invention is not limited to array lasers using cleavage planes. Depending on mounting considerations, it is also possible to employ, for example, a resonant surface formed by a wet process or a dry process on one side or both sides. Examples are shown in Figures 6 and 7.
Shown in the figure.

Each /l (7) In the figure, 213a to 213e, 22
Injection regions 3a to 223c each have independent injection electrodes.

214a to 214e, 215a to 215e (b.

(c and d are not shown) are the resonator surfaces formed by etching.

Figure 7 Nioite is 224a, 224b, 224c
, 225a, 225b, and 225c are resonator surfaces formed by etching.

Returning to the embodiment shown in FIG. 1 in which the resonator is formed with a cleavage opening, if the angle φ is too large, the angle of incidence on the resonant surface will increase and the reflectance will decrease, so the angle φ should be 11
A value within 5 degrees is appropriate. In particular, when φ is about ±3 degrees, the oscillation threshold current increases by about 10 to 20%, which is easy to drive.

Furthermore, it is possible to change the light emission angle θ to approximately ±lθ°.

Furthermore, it is generally convenient for device design to use constant values for the distance between lasers and the deviation 0 in the light emission direction. However, it is not necessarily necessary to take a constant value.

In addition, the material of the semiconductor laser is GaAseAJIGaA.
In addition to s type, I nPs I nGaAsP type, AMGa
Needless to say, the same applies to materials such as InP.

〔Effect of the invention〕

As explained above, the present invention has a superlattice structure as a part of each component, and uses MBE method or MOC method.
By employing a semiconductor laser manufactured by the VD method, it has become possible to extract high luminous efficiency and homogeneous output with good reproducibility in different emission directions.

By using an array laser with different light emission directions, it is possible to form a good image of laser light from many points on a medium using a scanning optical system, so it is suitable as a light source for optical devices such as laser beam printers. Extremely advantageous.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of a semiconductor device according to the present invention, FIG. 2 is a sectional view taken along line A-A' in FIG. 1, and FIG. 3 is a conventional example in which lasers are arranged in a hybrid manner. Fig. 4 shows a conventional example in which a 7-laser laser with a constant emission direction and a prism are combined to have different emission directions, and Fig. 5 shows a case where an array laser with a constant emission direction is corrected by an optical system. The diagram showing the conventional example, and FIGS. 6 and 7 are diagrams showing modifications of the present invention, respectively. 11-15... Semiconductor laser, 16.17...
...Resonance surface. )z21

Claims (1)

[Claims] (1) In a semiconductor laser device in which a plurality of semiconductor lasers are monolithically formed, each of the semiconductor lasers has a superlattice structure as a part thereof, and these semiconductor lasers emit light in mutually different directions. 1. A semiconductor laser device characterized in that it is formed by a molecular beam epitaxy method or a metal oxide vapor phase epitaxy method.