JPS62269384A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To perform a favorable image-formation of laser beams incoming from numerous points with the aid of an optical system of scanning by making the formation so that an active layer has multi-quantum wells and a semiconductor laser of these wells emits its beams in the different directions to one another. CONSTITUTION:Four laminations for N-type GaAs 22, N-type Al GaAs 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 of multi-quantum wells is formed by laminating GaAs and then, P-type Al0.4Ga0.8As 25 and GaAs 26 are formed according to 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 according to a plasma CVD system and only a 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-Ga 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]

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 are arranged so that the emission directions of the two intersect at one point Po, and the scanning spot (not shown) can be scanned with a plurality of scanning spots 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. Reference numerals 31a and 31b are semiconductor lasers, and each laser is arranged at the bottom of 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
The end surfaces 32a and 32b are set such that when normal lines are drawn to each of the end surfaces 32a and 32b at the position where b) is provided, each normal line passes through P. Furthermore, when viewed from a direction parallel to the deflection scanning plane, the mounting position is set so that the position where the central rays ha and hb of each semiconductor laser pass through the point P is slightly displaced in the direction perpendicular to the deflection scanning plane. 3
The position of the semiconductor laser provided in 21 is set. ”
- The point Po 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 (e.g. semiconductor lasers) so that their respective light emission directions are different, they must be aligned on the mount as shown in the example above to form 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), 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, as if PO
It is bent as if it had passed through. Same <41 b
The central ray hb from P 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 42e, 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 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 were exiting from the PO. . 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 set the distance below 1007 im.

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 a method in which a plurality of semiconductor lasers are formed monolithically, and each semiconductor laser is formed monolithically. A semiconductor device has already been proposed in which the laser beams are emitted in different directions.

[Summary of the invention]

The 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 form an optical system with a short optical path length. This will further improve performance.

The above object of the present invention is to provide a semiconductor laser device in which a plurality of semiconductor lasers are monolithically formed, wherein the active layer of each of the semiconductor lasers has a multiple quantum well structure, and these semiconductor lasers have a multi-quantum well structure. This is achieved by forming the structure so that the light is emitted 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, but in a broad sense, there is one set of lasers that emit light in different directions. This means that there are more than one set.

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

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

The specific solution proposed in the present invention is to improve the structure of a semiconductor laser by reducing the above-mentioned reduction in luminous efficiency according to US Pat.
．． This is achieved by improving the temperature characteristics of light emission by employing a multi-quantum well structure disclosed in Japanese Patent No. 207.

That is, by adopting the above structure as described in the following examples, (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) In the MQW structure, there is little change in light output with respect to constant temperature changes.

As a result of the combination of (1) and (2), 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.

The multi-quantum well structure can be used as an optical modulator by taking advantage of the fact that its absorption characteristics change with the injection of charge or the application of an electric field, and it can be used as a short-wavelength laser oscillation bistable by taking advantage of the fact that the effective band gap changes due to quantum effects. Although it is used in optical devices, etc., there is no example of a high-density oblique-emission laser device being made into a device by focusing on its high luminous efficiency and good temperature characteristics like the present invention, and it is necessary to adapt it to the usage format. The present invention was arrived at while pursuing the above.

〔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, ll-15 indicates an individual semiconductor laser, and lla to 15a correspond to a current injection region, that is, a light emitting region in each of the semiconductor lasers 11 to 15. The angles formed by the extension line of this injection region 11a-15a (hereinafter referred to as the resonance direction) flb-15b and the normal line 18 erected to the resonance surfaces 16 and 17 are φa, φb, φC1φd, and φe, respectively. It is formed like this.

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 / n □ = sin θ
/ sinφ holds true. For example, considering the case of emission from a GaAs crystal, n (the refractive index of the crystal) is approximately 3°5 and no (the refractive index of air) is approximately 1, so φ
If you choose at once, the laser beam will be about 3.5 with respect to the normal 18.
It emits at an angle.

In the embodiment shown in FIG. 1, φa, φb, φC1φd, φ
e respectively +1.0 degree, +0.5 degree, 0.0 degree, -
By setting it to 0.5 degrees, -i, o degrees, the output angle θ
a, θb, θC9θd, 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 AA' in FIG. 1. The manufacturing process will be described in detail below using this figure.

First, on an n-type GaAs substrate 21, 17 zm of n-type GaAs 22 was deposited as a buffer layer, 2 gm of n-type AuGaAs 23 was deposited as a cladding layer, and n-type AI was deposited as a cladding layer.
0.4 Ga O, 8A s 2gm, active layer made of non-doped GaAs 1OO, A pattern 0.2 Ga
0.8 A s 30 people repeated 4 times and finally GaAs
100 people were stacked. An active region 24 having a multiple quantum well structure was formed. Next, as a cladding, P type A n O, 4G
15 pm of a O,8A s 25 and 0.5 g of GaAs 26 as a cap layer were formed by molecular beam epitaxy.

Next, in order to limit the current injection region, as shown in FIG. 101, after etching the active layer 24 by 0.4 pLm, a silicon nitride film 27 is formed by plasma CVD, and only the top of the ridge is etched. This was used as the injection area.

The width of the implanted region is 3 gm, and it goes without saying that the same effect can be obtained even if the five stripes are replaced with Pan in each of the examples.

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

After scraping the GaAs substrate 21 to a thickness of 100 gm, the GaAs substrate 21 is used as an n-type ohmic electrode 29.
A u-Ge111t electrode was deposited.

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

Note that the pitch of each laser is 11 at the resonant surface 16.
It is 00k. On the other hand, each of the electrodes 1id-15d was taken out independently by wire bonding (not shown).

Here, the cavity length (distance between resonance surfaces 16 and 17) is 3
00 pm.

As a result, it was possible to monolithically form five lasers whose light emission directions differed by 1.75 degrees within the same plane.

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

Examples thereof are schematically illustrated in FIGS. 6 and 7.

Regarding the angle φ, if the angle φ is too large, the angle of incidence on the resonant surface becomes large and the reflectance decreases, so it is appropriate that the angle φ is within ±15 degrees.

Particularly, when φ reaches 13 degrees, the oscillation threshold current increases by about 10 to 20%, making it easy to drive. Moreover, it is possible to change the light emission angle θ to about ±10′.

In this example, a GaAs system was used and a ridge wave structure was used as an example. It is also effective against lasers. It is also effective for gain waveguide type lasers such as stripe electrode type and proton bombarded type lasers.

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 material of the semiconductor laser is GaAs/AMGaAs.
In addition to the I nPe I nGaAsP system, AJIGa
Needless to say, the same applies to materials such as Inp-based materials.

〔Effect of the invention〕

As explained above, the present invention has the effect of being able to create a multi-dimensional array laser with a small output fluctuation regardless of the output history and different light emission directions using the MQW structure. 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 tried to be corrected by an optical system. Figures illustrating examples, FIGS. 6 and 7, each illustrate a modification of the present invention. 11-15---One semiconductor laser, 16.17---Resonance surface.

Claims (1)

[Claims] (1) In a semiconductor laser device in which a plurality of semiconductor lasers are monolithically formed, the active layer of each of the semiconductor lasers has a multiple quantum well structure, and these semiconductor lasers emit light in mutually different directions. A semiconductor laser device characterized in that it is formed so as to.