JPS62268184A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain excellent luminous characteristics by uniformly forming a fourth semiconductor layer at equal distances from an active layer or shortening a distance between the fourth semiconductor layer and the active layer, effectively giving a distribution of refractive index and confining beams to a striped shape. CONSTITUTION:Substrate N-GaAs 101, clad-layer N-Al0.45Ga0.55As 102, active- layer GaAs 103, clad-layer P-Al0.45Ga0.55As 104 and N-Al0.45 Ga0.55As 105 having a current constriction effect are shaped in succession, and light-absorption layer N-GaAs 112 is formed. N-Al0.45 Ga0.55As 105 and N-GaAs 112 are removed to a striped shape up to P-Al0.45Ga0.55As 104, and P-Al0.45Ga0.55As 107 and contact-layer P-GaAs 108 are grown regarding an optical guide layer 106. Electrodes are shaped by Au-Zn/Au 109 and Au-Ge-Ni/Au 110 regarding whether P type or N type, and a cavity is formed through cleavage, thus manufacturing a laser. Accordingly, luminous characteristics can be improved.

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 Japanese Patent Application Laid-Open No. 59-126, light is emitted from a light emitter as shown in FIG. The emission direction is one point P.

The light sources were designed such that the light sources intersected at the same angle, and the scanning spot (not shown) could 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. 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. Mount 32 provided with semiconductor lasers 31a and 31b
The end surfaces 32a and 32b are at a point P where the central rays ha and hb of the diverging light beams from the respective lasers 31a and 31b are the same. It is set as if it had passed through.

In other words, if normal lines are drawn to the end faces 32a and 32b at the positions where the semiconductor lasers (31a, 31b) are provided, each normal line is P. The end faces 32a and 3
2b is set. Furthermore, when viewed from a direction parallel to the deflection scanning plane, the central rays ha and hb of each semiconductor laser
The position of the semiconductor laser provided on the mount 32 is set so that the position passing through 20 points is slightly displaced in a direction perpendicular to the deflection scanning plane. Above P. The point P in a predetermined vicinity of the deflection reflection surface 33 of the deflector is 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, 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. 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, 41
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 the central ray ha of the luminous flux is refracted as if by P. It is bent as if it had passed through. Similarly, the central ray h from 41b
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 42e, as if P.

It is bent as if it had passed through. Note that the central ray ha from 41c passes through the plane 42c perpendicularly, and P is on the extension line of this central ray hc. exists.

In this way, an inclined plane with a defined inclination angle is provided corresponding to each light emitting section, and the center ray of each luminous flux after exiting the prism 42 is as if P. Its direction is controlled as if it were emitted from a source. This P. As described above, is maintained conjugate to 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 array laser 41, and the smaller the pitch of the array laser, the more difficult it becomes. In fact, it is almost impossible if the thickness is less than 100 μm.

On the other hand, FIG. 5 shows an optical system, that is, a relay optical system 53, which is intended to have a similar effect.
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 monolithically formed, and each semiconductor laser A semiconductor device has already been proposed in which the directions of emission are different.

[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 lenses etc. to construct an optical system with a short optical path length. This will further improve the

A semiconductor laser device according to the present invention is a semiconductor device in which a plurality of semiconductor lasers are formed into a monolink.
The semiconductor laser described above is characterized in that the directions of light emitted from the respective resonant surfaces are different.

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 a serious problem 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 presented in the present invention is to prevent the above-mentioned reduction in luminous efficiency by forming a first semiconductor layer, which serves as an active layer, in each semiconductor laser so that the forbidden band interval is larger than that of the first semiconductor layer. a fourth semiconductor layer sandwiched between second and third semiconductor layers having a small refractive index and having a forbidden band interval between the first semiconductor layer and the second and third semiconductor layers; In close proximity to the active layer, a fourth semiconductor layer is formed substantially equidistantly and substantially uniformly from the active layer, or a fourth semiconductor layer corresponding to the current main region is formed.
By forming the distance between the fourth semiconductor layer and the active layer to be shorter than the distance between the other active layer and the fourth semiconductor layer, it is possible to effectively provide a refractive index distribution and confine light in a striped pattern. In other words, by adopting the above structure as described in the examples below, (1) the injection current required for light emission is reduced, and the same level of light output is achieved. The amount of heat generated to obtain the desired performance is reduced, resulting in a lower operating temperature.

(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.

(4) Because it passes through a semiconductor waveguide layer with a bandgap larger than the oscillation wavelength, there is less absorption (the edge destruction output is improved,
A high output device can be obtained.

Due to the above-mentioned combined effects, good light emission characteristics can be obtained regardless of the light emission history 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.

FIG. 1 shows an embodiment of the present invention. In the figure, 11 to 15 indicate individual semiconductor lasers, and Ila to 15a correspond to current injection regions, that is, light emission regions in each of the semiconductor lasers 11 to 15. The angles formed by the extension lines of the injection regions 11a to 15a (hereinafter referred to as resonance directions) llb to 15b and the normal line 18 to the resonance surfaces 16 and 17 are φa, φb, φC9φd, and φe, respectively. It is formed like this.

Note that the resonance planes 16 and 17 are parallel because the cleavage planes of a crystal (e.g., GaAs) that is normally used as a substrate are used, but in cases where the parallelism may be slightly different, 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, 1lc-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(,=sinθ/si
The relationship nφ holds true. For example, considering the case where the light is emitted from a GaAs crystal, n (the refractive index of the crystal) is approximately 3.5, and n
Since o (the refractive index of air) is about 1, if φ is chosen to be 1 degree, the laser beam will be emitted at an angle of about 3.degree. and 5.degree. with respect to the normal 18.

In the embodiment shown in FIG. 1, φa, φb, φC2φd, φ
e is +1.0 degree, +0.5 degree, and 0.0 degree, respectively.

By setting -〇, 5 degrees, -1, 0 degrees, the output angles θa, θb, θC9θd, θe will be +3゜5, respectively.
Every time.

+1.75 degrees, 0.0 degrees, -1.75 degrees, -3
, 5 degrees.

FIG. 6 is a sectional view taken along line A-A' in FIG. 1.

The manufacturing process will be described in detail below using this diagram.

FIGS. 6(a) and 6(b) show examples of the present invention. In FIG. 6(b), 101 is the n-G substrate.
It is aAs. 102 is a cladding layer n-Al1o
, 45GaO-55As and has a thickness of 1.5 μm. 103 is the active layer undoped
It is GaAs. The thickness is 0.05-01 μm. 1
04 is the cladding layer p A l O, 45Ga
The thickness of the 55 As is 0.2 to 0.3 μm. Furthermore, on top of this, n-A l having a current confinement effect
, ), 45 Ga O, 55 As was formed with a thickness of 0.7 μm, and 112 light absorption layers were formed with n-GaAs with a thickness of 0.5 μm.
Formed. Thereafter, by etching, a p kl of 104 was formed as shown in FIG. 6(a). , 45caO-55A
n-AAo of 105.112 in stripe shape up to s,
45Ga, ), 55As, and n-GaAs. After this removal, the optical waveguide layer 106 of 106 was removed.
Formed with a thickness of 2 μm. This layer is p A l-0-35G
a 0-65As, and guides light that spreads from the active layer to the cladding layer. Furthermore, on top of this, 107 p-A
fO, 45GaO, 55As is formed to a thickness of 1.5 μm, and p-GaAs of 108 is grown thereon as a contact layer. In order to make a laser, the electrode should be made of p-type or n-type, and 109 is Au-Zn/Au11O is Au-G.
Formed by e-Ni/Au, with pleats 350
Create a μm cavity and use it as a laser. The width of the waveguide layer 113 is suitably 1.5 to 3 μm in order to obtain a single transverse mode.

The advantages of this configuration are as follows: (1) The light emitting area is wider than the active layer, which improves the output limit at which end face destruction occurs.

■ The waveguide layer is guided by the refractive index both vertically and horizontally, resulting in good optical confinement in a single transverse mode.■ Current confinement is formed using a P-N junction, making it possible to form a highly efficient laser.

Note that this example uses an n-GaAs substrate, but a p-GaAs substrate is used.
GaAs may also be used. At this time, it is sufficient to reverse the current polarity of the layers to be laminated.

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 2-1 and 2-2.

213a to 213e, 223a in each figure
223c is an injection region, each having an independent injection electrode. 214a ~ 214e, 215a ~
215e (b.

(c, d not shown) are the resonator surfaces formed by etching. Moreover, in FIG. 2-2, it is 224a.

224b, 224c, 225a, 225b,
225c is a resonator surface formed by etching.

It should be noted that the first semiconductor layer, which is the active layer shown in the claims, and the second semiconductor layer sandwiching the first semiconductor layer are the active layers. In the third semiconductor layer structure, the second. The third region includes a superlattice structure that is not an active layer and a semiconductor layer whose composition is continuously changed;
A generation layer is a region where carrier recombination mainly occurs and a region of several thousand Å formed adjacent to the region where carrier recombination occurs.
It also contains a thin layer of: For example, a single quantum well (and multiple quantum wells, and a typical layer of about 0.1 μm)
It includes a barrier layer of several to several thousand layers formed on both sides of the light, and a thin layer of 0.1 μm or less that causes light confinement.

〔Effect of the invention〕

As explained above, the present invention has made it possible to extract a uniform output with high luminous efficiency and high reproducibility from different emission directions in a conventional semiconductor laser device. Furthermore, since the light emitting direction from each laser is different, laser beams from multiple points can be imaged well on the medium using a scanning optical system, making it suitable as a light source for optical devices such as laser beam printers. Extremely advantageous.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a plan view showing an embodiment of a semiconductor device according to the present invention, FIGS. 1-1 and 2-2 are plan views showing a modification of the present invention, and FIG. Fig. 4 shows 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 an array laser with a fixed emission direction. FIGS. 6(a) and 6(b) are schematic cross-sectional views each showing an example of the configuration of a semiconductor laser. 11-15... Semiconductor laser, 16,
17...Resonance surface.

Claims (1)

[Claims] (1) A plurality of semiconductor lasers are formed monolithically, and each semiconductor laser has a first semiconductor layer serving as an active layer, which has a larger forbidden band interval and a lower refractive index than the first semiconductor layer. a fourth semiconductor layer sandwiched between the second and third semiconductor layers, having a forbidden band interval intermediate between the first semiconductor layer and the second and third semiconductor layers; The fourth semiconductor layer corresponding to the current injection region and the active layer are formed substantially uniformly at substantially the same distance from the active layer, or the distance between the fourth semiconductor layer and the active layer corresponding to the current injection region is changed from that of the other active layer and the fourth semiconductor layer. By forming the laser diode to be shorter than the distance between the laser diode and the laser diode, it is configured to effectively provide a refractive index distribution and confine light in the form of a stripe. ,
A semiconductor laser device characterized by emitting multiple lights in different directions.