JPH0552679B2 - - Google Patents

Description

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

[Conventional technology and problems]

Conventionally, when designing an optical scanning device using a plurality of semiconductor lasers or light emitting diodes (LEDs), as disclosed in JP-A-59-126, for example, the light emitted from the light emitting body is The light sources were arranged so that their emission directions intersected at one point _P0 , and the scanning surface (not shown) could be scanned with a plurality of scanning spots while maintaining good imaging conditions.

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 31
The end faces 32a, 32b of the mount 32, on which the lasers 31a, 31b are provided, are set so that the central rays ha, hb of the diverging light beams from the respective lasers 31a, 31b pass through the same point _P0 . In other words,
If normal lines are drawn to the end faces 32a and 32b at the positions where the semiconductor lasers 31a and 31b are provided,
The end faces 32a and 32b are set so as to pass through each normal line _P0 . Furthermore, the mount 32 is arranged so that, when viewed from a direction parallel to the deflection scanning plane, the positions where the central rays ha, hb and point _P0 of each semiconductor laser pass are slightly displaced in a direction perpendicular to the deflection scanning plane. The position of the semiconductor laser provided above is set. The above P ₀ point and the deflection reflection surface 3 of the deflector
The imaging lens 34 maintains an optically conjugate relationship with a point P in a predetermined vicinity of No. 3.

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, they must be aligned on the mount and configured into a hybrid structure, as shown in the example above. I needed to. 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. Japanese Unexamined Patent Publication 1983-
In an example disclosed in US Pat. No. 2,112,735, 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, 4
1d and 41e, and 42 is a prism. The central ray ha of the luminous flux from the light emitting part 41a is refracted by the inclined surface 42a and is bent as if it had passed through _P0 . Similarly, the central ray hb from 41b is bent by the inclined surface 42b, the central ray hd from 41d is bent by the inclined surface 42d, and the central ray he from 41e is bent by the inclined surface 42e, as if they had passed through P ₀ . It will be done. Note that the central ray hc from 41c passes through the plane 42c perpendicularly, and P ₀ exists on an extension of this central ray hc.
In this way, an inclined plane with a defined angle of inclination is provided corresponding to each light emitting part, and the direction of the central ray of each luminous flux after exiting the prism 42 is controlled as if it had exited from P ₀ . There is. As mentioned above, this P ₀ is the desired position P near the deflection reflection surface.
(not shown) and is maintained conjugate through an optical system.

Problems in this case include the accuracy and method of microfabrication of the prism 42, the alignment and joining method of the prism 42 and the array laser 41, and the smaller the pitch of the array laser, the more difficult it becomes. actual,
It is almost impossible if the thickness is less than 100 μm.

On the other hand, FIG. 5 shows a similar effect in an optical system, that is, a relay optical system 53, which uses a collimator lens 52 and a cylindrical lens 55 to collimate and image the light emitted from array lasers 51a and 51b. This is an example in which an image is formed on a polygon surface 54 with a relay optical system 53 interposed therebetween, and the image is formed on a scanned surface (not shown) in a good image formation state.

The problem in this case is the optical path length, and the relay system itself becomes about 20 cm longer.

It is an object of the present invention to eliminate alignment errors and limitations on integration density caused by arranging semiconductor light emitters in a hybrid, and also to eliminate alignment errors and limitations in integration density caused by arranging semiconductor light emitters in a hybrid, as well as to eliminate alignment errors and limitations in integration density, such as when using a monolithically formed array laser with a constant light emission direction. An object of the present invention is to provide a semiconductor device that makes it possible to avoid the complexity of an additional optical system.

[Means for solving problems]

A semiconductor device according to the present invention is a semiconductor device in which a plurality of semiconductor lasers are monolithically formed, and the semiconductor lasers are formed such that the angles formed between the resonance direction and the resonance plane of each of the semiconductor lasers are different,
A feature is that the light emitted from each of these semiconductor lasers is emitted from a different direction at the point in time when the light is emitted from the resonant surface.

In addition, the expression "the directions of light emitted from each laser are different" used in the following description does not mean that there is no set of lasers that emit light in the same direction, but in a broad sense, there is a set of lasers that emit light in different directions. This means that there are more than one.

〔Example〕

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

FIG. 1 shows an embodiment of the present invention. In the figure, 11
~15 indicate individual semiconductor lasers, 11a~1
5a corresponds to a current injection region, that is, a light emitting region in each of the semiconductor lasers 11 to 15. Then, extension lines (hereinafter referred to as resonance directions) of the injection regions 11a to 15a 11b to 15b and resonance surfaces 16 and 1
The angles formed with the normal line 18 set at 7 are φa and
They are formed to have φb, φc, φd, and φe.
Here, the injection regions 11a to 15a have a higher gain due to current injection, and constitute a so-called gain type optical waveguide. Semiconductor laser 11, 12, 1
4 and 15, the longitudinal direction of the injection region is non-perpendicular to the normal 18 of the resonant surface, so the light generated by each semiconductor laser is reflected at the resonant surface in a direction different from the longitudinal direction of the injection region. be done. however,
As described above, since the injection region constitutes an optical waveguide, a portion of the reflected light returns to the injection region due to the optical confinement effect and travels backward through the injection region. In this way, laser oscillation occurs due to stimulated emission of light reflected by the resonant surfaces 16 and 17 and traveling back and forth in the injection region.

Note that the resonance planes 16 and 17 are usually parallel because the cleavage planes of a crystal (for example, GaAs) used as a substrate are used, but in cases such as dry etching where the degree of parallelism may be slightly different, Consider the resonant surface 16 on the laser emission front side 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 approximately according to Snell's law. In the figure, 11c to 15c
indicates the light emission direction.

Here, if the angle formed between any light emission direction and the normal line 18, that is, the emission angle is θ, then n/n ₀ =
The relationship sinθ/sinφ holds true. For example, if we consider the case of emission from a GaAs crystal, n (crystal and refractive index)
is about 3.5, and n ₀ (the refractive index of air) is about 1, so
If φ is selected to be 1 degree, the laser beam will be emitted at an angle of approximately 3.5 degrees with respect to the normal line 18.

In the embodiment shown in FIG. 1, φa, φb, φc, φd,
φe is +1.0 degree, +0.5 degree, 0.0 degree, -0.5 degree, -, respectively.
By setting it to 1.0 degrees, the output angles θa, θb, θc,
θd, θe are +3.5 degrees, +1.75 degrees, 0.0 degrees, -, respectively.
We were able to create an array laser with angles of 1.75 degrees and -3.5 degrees.

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

First, on an n-type GaAs substrate 21, a buffer layer of n-type GaAs 22 of 1 μm, a cladding layer of n-type AlGaAs 23 of 2 μm, an active layer of non-doped GaAs 24 of 0.08 μm, and a cladding layer of 0.08 μm are deposited.
P ⁺ type AlGaAs25 with a thickness of 1.5 μm as a cap layer.
GaAs26 was made to a thickness of 0.1 μm by molecular beam epitaxy.

Next, in order to limit the current injection region, plasma
After a silicon nitride film 27 was deposited to a thickness of 0.2 μm by the CVD method, a portion of the silicon nitride film (regions 11a to 15a in FIG. 1) was removed by a photolithography process. The stripe width (width W of the implanted region) is 5 μm. Furthermore, each of the five stripes is formed at an angle of 0.5 degrees.

Next, a Cr-Au ohmic electrode is formed as the upper electrode, separated by etching, and etched into 11d to 15d.
There were five independent electrodes.

In addition, after the GaAs substrate 21 is scraped to a thickness of 100 μm by wrapping, an ohmic electrode 29 for n-type is formed.
An Au-Ge electrode was then deposited.

Subsequently, after a heat treatment for diffusion was performed, the resonant surfaces 16 and 17 were cleaved as shown in FIG. 19 surfaces were separated using a scribe.
Note that the pitch of each laser is 100 μm at the resonant surface 16. On the other hand, each of the electrodes 11d to 15d was independently taken out by wire bonding (not shown). Here, the cavity length (the distance between the resonant surfaces 16 and 17) is 300 μm.

This allows the light output direction to be adjusted within the same plane.
We were able to monolithically form five lasers that differ by 1.75 degrees.

Generally, in order to vary the light emission direction of a semiconductor laser while keeping the injection region (resonance direction) and the resonance plane perpendicular, the resonance plane must be formed with an angle equal to the deviation θ in the light emission direction. In this case, since the resonant surface cannot be formed linearly, it is impossible to use the conventionally established cleavage technique. Therefore, it is necessary to form by dry process etching or the like using a photomask that is shifted by θ. In this case, problems arise such as the resonant surface becomes non-uniform and the reflectance decreases, and the oscillation threshold current increases because the 16 resonant surfaces cannot be formed perpendicularly to the surface of the active layer 24. . According to the semiconductor device according to the present invention, since the angles between the resonance direction of each laser and the resonance plane are different as described above, the resonance plane can be formed by cleavage, and such a problem does not occur.

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 resonant surfaces formed by a wet process or a dry process on one or both sides, for example.

Regarding the angle φ, if it is too large, the angle of incidence on the resonant surface will increase and the reflectance will decrease, but if the angle φ is around ±3 degrees, the oscillation threshold current will only increase by about 10 to 20%. , easy to drive. Moreover, it is possible to change the light emission angle θ to about ±10°.

Although this example uses a GaAs-based stripe electrode laser (a type of gain waveguide laser) as an example, it is also applicable to other gain waveguide types, such as a proton bombarded type laser. It is also effective for refractive index guided lasers such as , BH structure, and rigid wave structure.

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

In addition, the semiconductor laser material is GaAs.
Needless to say, the same applies to materials such as InP/InGaAsP and AlGaInP in addition to AlGaAs.

〔Effect of the invention〕

As explained above, the present invention is formed so that the angle formed between the current injection region (resonance direction) and the resonant surface changes little by little. A monolithic structure has the advantage that it is possible to create an array laser. In addition, by using array lasers with different light emission directions, it is possible to form good images of laser light from many points on the medium using a scanning optical system, so it is possible to form a good image on the medium using a scanning optical system. This is 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 an array laser with a fixed emission direction and a prism are combined to have different emission directions, and FIG. 5 shows a conventional example in which an array laser with a fixed emission direction is attempted to be corrected by an optical system. 11-15... Semiconductor laser, 11b-15b
... Resonance direction, 16, 17 ... Resonance surface, 11c ~
15c...Light emission direction.

Claims (1)

[Claims] 1. A plurality of semiconductor lasers are monolithically formed on the same substrate, and each laser includes a semiconductor layer including an active layer laminated on the substrate, and a semiconductor layer provided on the semiconductor layer. In the semiconductor device, each of the electrodes has a pair of light emitting end faces, an electrode provided independently of another laser, and a striped region into which a current is injected by the electrode. The laser is formed from the one end face to the other end face, and the current injection region of at least one laser among the plurality of lasers is set so that the longitudinal direction thereof is within 3 degrees from the normal to the end face. By forming the beams so that they intersect at an angle, the angle between the light emission direction of the at least one laser and the normal to the end surface is the same as the longitudinal direction of the current injection region of the at least one laser and the normal to the end surface. What is claimed is: 1. A semiconductor device, characterized in that the angle is larger than the angle formed with the normal line, and the light emission direction of the at least one laser is non-parallel to the light emission direction of the other lasers.