JP2921239B2 - Multi-beam semiconductor laser and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser, and more particularly to a multi-beam semiconductor laser having a plurality of beams which can be driven independently on the same semiconductor chip, and a method of manufacturing the same.

[0002]

2. Description of the Related Art At present, semiconductor lasers are widely used in laser printers and optical disks, but the drawing speed of the printer and the data transfer speed of the optical disk are not always sufficiently high. In this case, if two beams that can be driven closely and independently can be emitted from one semiconductor laser, a system having a double drawing speed or data transfer speed can be created with one optical system. Because of this, research on such a multi-beam semiconductor laser has recently been conducted. This type of laser currently used has an AlGaAs wavelength of 0, 78-0, 84 μm.
In each case, an active layer grown separately for each beam is embedded.

[0003]

As described above, the conventional multi-beam semiconductor laser is of the AlGaAs type.
If this can be replaced with a GaInP or AlGaInP type having a wavelength of 0, 6 to 0, or 7 μm, there can be expected advantages that a photosensitive material with higher sensitivity can be used and a light spot can be easily narrowed down.

However, in the case of using these materials, Al
Unlike the case of the GaAs system, a structure in which an active layer divided for each beam is embedded cannot provide characteristics sufficient for crystal growth.

The inventor of the present invention has proposed a GaInP device in which the active layer is made common, the contact layer is divided into individual beams by etching, and the injected current is guided from the contact layer to the stripe portion of each beam by the action of the current blocking layer. Prototype multi-beam semiconductor laser.

[0006] In the prototype multi-beam semiconductor laser, it was confirmed by a scanning electron microscope that the contact layer at the separation part of each beam was almost completely removed by etching, and almost no contact layer remained between the beams. Even if it remains, it is so small that it cannot be confirmed with a scanning electron microscope (200 angstrom or less), and the current flowing therethrough should be negligible.

Nevertheless, in this multi-beam semiconductor laser, a large current crosstalk was observed, and when one of the beams was oscillated, light emission was observed from the other, although weakly. When the resistance between the p-electrodes (electrodes separated from each other) of the two beams was measured, it was as small as about 10Ω.

An object of the present invention is to provide a multi-beam semiconductor laser with less crosstalk.

[0009]

According to the present invention, there is provided a multi-beam semiconductor laser insulated in a bottomed groove having a depth reaching halfway of a current block layer for guiding an injection current from a contact layer to a stripe portion of each beam. A separation section made of a body is provided, and the contact layer is separated for each beam by the separation section.

Further, according to the method of manufacturing a multi-beam semiconductor laser of the present invention, after forming an active layer, a current blocking layer and a contact layer, a portion between the beams of the contact layer is removed, and a current blocking layer below the contact layer is removed. A step of performing an inter-beam etching to partially remove the lower part while leaving the lower part, and, after the inter-beam etching step, embed an insulator in a space removed by etching of the contact layer and the current blocking layer to separate the part. And forming a.

[0011]

In the GaInP-based multi-beam semiconductor laser prototyped above, the surface exposed to the atmosphere after growing the current blocking layer directly connects the beams, and the current passes through the impurities to generate crosstalk. It is thought to have occurred. On the other hand, in the present invention, since the surface of the current block layer is insulated and separated by the insulator of the separating portion, crosstalk is drastically reduced.

[0012]

FIG. 1 is a sectional view of a multi-beam semiconductor laser showing one embodiment of the present invention. In the figure, 1 is a GaAs substrate to which Si is added, and 2 is a Ga to which Si is added.
Buffer layer made of As layer, 3 is AlG to which Se is added
aInP cladding layer, 4 is undoped GaIn
The active layer made of P is made of AlGaInP doped with Zn.
6 is a current blocking layer made of GaAs to which Si is added, and 7 is a GaI layer to which Zn is added.
3 shows a cap layer made of nP. Reference numeral 8 denotes a contact layer made of GaAs to which Zn is added.
Indicates a p-electrode and an n-electrode, respectively. Reference numeral 11 denotes a silicon nitride film formed so as to fill a groove for separating beams.

FIG. 1 schematically shows the structure.
The dimensional ratio of each part does not always represent the dimensional ratio in an actual element. For example, in practice, the thickness of the GaAs substrate 1 is 7
While the thickness is about 0 μm, the total thickness from the buffer layer 2 to the cap layer 7 thereon is about 2 to 3 μm, and the thickness of the contact layer 8 thereover is about 2 μm.

The active layer 4 is commonly formed for each beam, but each beam is formed by an insulating silicon nitride film 11 formed so as to fill a groove formed by etching from the contact layer 8 to the current block layer 6. Are separated.

Next, a method for manufacturing such a multi-beam semiconductor laser will be described with reference to FIGS.

On a GaAs substrate 1, a buffer layer 2, a cladding layer 3, an active layer 4, a cladding layer 5, and a cap layer 7
Are sequentially epitaxially grown, and then the silicon nitride film 2
1 is formed (FIG. 2A). This silicon nitride film 21
Is patterned so as to be used as a mask when the portion shown by the broken line is removed by etching in the next step.

Then, after performing mesa etching (FIG. 2B), a current blocking layer 6 is grown on that portion (FIG. 2C). After that, the silicon nitride film 21 is removed,
A contact layer 8 is grown on the entire surface (FIG. 2D).

Next, a patterned silicon nitride film 22 is formed (FIG. 2 (e)), and using this as a mask, etching for electrically separating each beam is performed.
The silicon nitride film 22 is removed (FIG. 2F). The etching is performed so as to remove the contact layer 8 and further remove a part of the current block layer 6 thereunder. If this etching is further advanced until the current penetrates the current blocking layer 6 and reaches the cladding layer 5 thereunder, a small amount of current passes through the exposed surface, and some crosstalk occurs again. For this reason, this isolation etching is applied to the current blocking layer 6, but it is desirable to keep the isolation etching at a depth not reaching the cladding layer 5.

Thereafter, a silicon nitride film 11 'and a resist film 23' are formed on the entire surface (FIG. 3A), and the resist film 23 'is patterned by photolithography. Etching the film 11 'to form the silicon nitride film 1
Leave only one. (FIG. 3 (b)).

Further, after a metal film 9 'made of a Ti / Pt / Au three-layer film is formed on the entire surface (FIG. 3 (c)), an excess portion is removed by etching to form a p-electrode 9. The resist pattern 23 is also removed (FIG. 3D). Finally, an n-electrode 10 made of an AuGe / Ni / Au three-layer film is formed on the back surface (FIG. 3E).

Regarding the multi-beam semiconductor laser fabricated in this manner, even if one of the beams is oscillated, no light emission from the other is observed, and the resistance between the p-electrodes 9 of each beam is as large as about 2000Ω. Was.

[0022]

As described above, according to the present invention, not only the contact layer is divided for each beam, but also the current blocking layer is provided with a separating groove, so that a multi-beam with less crosstalk can be obtained. can get. In particular, it is difficult to form a structure in which an active layer divided for each beam is embedded.
It is useful for nP or AlGaInP-based lasers, and has the effect that a multi-beam semiconductor laser having a shorter wavelength can be used as compared with AlGaAs-based lasers.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a multi-beam semiconductor laser showing one embodiment of the present invention.

FIG. 2 is a process sectional view showing the manufacturing method according to one embodiment of the present invention.

FIG. 3 is a process sectional view showing the manufacturing method according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... GaAs substrate, 4 ... active layer, 5 ... clad layer, 6 ...
Current block layer, 8 contact layer, 9, 10 electrode.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-56986 (JP, A) JP-A-61-248584 (JP, A) JP-A-1-186691 (JP, A) 1990 (Heisei 2) Year) Spring 37th Annual Meeting of the Society for Response Science 28a-SA-6 p. 906 (58) Field surveyed (Int. Cl. ⁶ , DB name) H01S 3/18 H01L 33/00

Claims (2)

(57) [Claims] 1. A multi-beam semiconductor laser having a plurality of beams which can be driven independently of each other on the same semiconductor chip and having a current blocking layer for guiding an injection current from a contact layer to a stripe portion of each beam. A multi-layer structure, comprising: a separating portion made of an insulator embedded in a groove having a depth up to an intermediate portion of a current block layer provided between each beam and dividing a contact layer for each beam. Beam semiconductor laser. 2. After forming an active layer, a current blocking layer, and a contact layer on a semiconductor substrate, a portion between beams of the contact layer is removed, and a part of a current blocking layer below the contact layer is left in the middle while leaving a lower portion. Performing a beam-to-beam etching to remove up to, and after the beam-to-beam etching process, forming a separation portion by burying an insulator in a space portion removed by etching the contact layer and the current blocking layer. 2. The method for manufacturing a multi-beam semiconductor laser according to claim 1, wherein: