JPH02106986A - Phase-lock semiconductor array - Google Patents

Abstract

PURPOSE:To change effective index distribution in a laser oscillation wavelength, and to make the gains of a fundamental super-mode larger than those of other super-modes by forming end-section disordering regions having refractive indices smaller than the refractive indices of disordering regions on the outsides of the disordering regions positioned at both striped end sections. CONSTITUTION:A plurality of disordering regions 31 are disposed into a superlattice optical guide 26 to a stripe shape. The disordering regions 31 are shaped by the disordering of a superlattice by implating the ions of Si as an impurity. End-section disordering regions 32 are formed near both end sections of the disordering regions 31 arranged to the stripe shape. This region 32 is doped with Si ions in concentration higher than the disordering regions 31 and promoted in disordering in the end-section disordering regions 31, and the refractive indices of the regions 32 are set so as to be made smaller than the refractive indices of the disordering regions 31. The disordering regions 31 and the end-section disordering regions 32 are brought to an N type by implanting Si ions, and an internal current constriction and an index waveguide mechanism are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a phase-locked semiconductor laser array that forms a refractive index waveguide mechanism by disordering a superlattice structure by diffusion of impurities.

(Prior art) Conventionally, as a technology in this field, Japanese Patent Application Laid-Open No. 62-1
There was one described in Publication No. 4488. The configuration will be explained below using figures.

FIG. 2 is a sectional view showing an example of the configuration of a conventional phase-locked semiconductor Kaeser array (hereinafter simply referred to as a laser array) described in the above-mentioned document.

In the figure, an n-type GaAs semiconductor substrate 10 includes:
n-type Ga 0.4 A 'J □, 6 A S lower cladding layer 2, undoped GaA s/G ao, 3
A, Ilo, y AS active layer 3-p type Gao
4 A, ll o, 2 A S optical waveguide layer 4, undoped G ag, g5AN o, o5A S/G a
g, 3A Do, 7A S superlattice optical waveguide layer 5,
An n-type Gao, 3A, llo, 7A S upper cladding layer 6 and an n-type GaAs cap layer 7 are sequentially formed. The cap layer 7 is formed in a stripe shape, and a diffusion region 8 in which impurities are diffused is formed in the upper cladding layer 6 and the superlattice optical waveguide layer 5 under the stripe gap. In the diffusion region 8 of the superlattice optical waveguide layer 5, the superlattice is disordered, and disordered regions 9 are formed in a stripe shape.

In the disordered region 9, the superlattice is disordered by impurities, and its electrical resistance is lower than that of the non-disordered superlattice optical waveguide layer 5. Therefore, only the part of the active layer 3 below the disordered region 9 becomes the gain region. Also,
Since the refractive index of the disordered region 9 is smaller than that of the non-disordered portion, the non-disordered superlattice optical waveguide layer 5 serves as a waveguide region. That is, the gain region and the waveguide region exist separately.

Electrodes 10 and 11 are provided on the lower surface of the semiconductor substrate 1 and on the upper surfaces of the upper cladding JI 6 and the cap layer 7, respectively, forming a laser array.

The laser array constructed as described above is manufactured in the following manner.

First, on a semiconductor substrate 1, a lower cladding layer 2 with a film thickness of about 1.5 μm, an active layer 3, and an optical waveguide J with a film thickness of about 0.2 μm are formed.
N4, superlattice optical waveguide layer 5 with a film thickness of about 0.7 μm, film thickness 1
An upper cladding layer 6 with a thickness of about .mu.m and a cap layer 7 with a thickness of about 0.2 .mu.m are sequentially formed using metal organic vapor phase epitaxy.

Next, impurities such as Zn are diffused using the striped cap layer 7 as a mask to form the upper cladding layer 6.
Then, a diffusion region 8 is formed in the superlattice optical waveguide layer 5 . At this time, in the diffusion region 8 in the superlattice optical waveguide layer 5, the superlattice is disordered by the impurity, and a disordered region 9 is formed. This disordered region 9 forms a stripe shape corresponding to the chap layer 7.

After that, the lower surface side of the semiconductor substrate 1 and the upper cladding layer 6
By providing electrodes 10 and 11 on the top surface of the cap layer 7 and the cap layer 7, a desired laser array can be obtained.

(Problems to be Solved by the Invention) However, in a phase-locked semiconductor laser array having a -F configuration, it is difficult to obtain a single fundamental supermode oscillation, and the highest order supermode oscillation with a bimodal far-field pattern is difficult to obtain. The problem was that I could only get it.

In other words, in order to obtain fundamental supermode oscillation from a phase-locked semiconductor laser array with the above configuration, it is necessary to perform delicate submicron microfabrication, and microfabrication as a practical industrial production method reliably achieves fundamental supermode oscillation. It was extremely difficult to obtain mode oscillation.

The present invention provides a phase-locked semiconductor laser array that solves the problem of the prior art, which is that it is difficult to obtain single fundamental supermode oscillation.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides at least a lower cladding layer, an active layer, a superlattice optical waveguide layer, and an upper cladding layer that are sequentially formed on a semiconductor substrate. In a phase-locked semiconductor laser array in which a disordered region formed by disordering of its superlattice in a wave layer is arranged in a stripe shape, outside the disordered region located at both ends of the stripe shape, An end disordered region having a refractive index smaller than that of the disordered region is formed.

The edge disordered region may be, for example, un+, lt! It can be easily formed by ion-implanting a substance and making the impurity concentration higher than that of the disordered region.

(Function) According to the present invention, since the phase-locked semiconductor laser array is configured as described above, the edge disordered region is located at both ends of the striped disordered region and has a refractive index smaller than that of the striped disordered region. The region acts to make the gain of the fundamental supermode larger than that of other supermodes by changing the effective lateral refractive index distribution at the lasing wavelength (this ensures that the fundamental supermode oscillation A unimodal far-field image can be obtained.

Further, the refractive index of the end disordered region can be easily lowered by supplying impurities by ion implantation and making the amount of impurity supplied larger than that of the disordered region.

Therefore, the above problem can be solved.

(Embodiment) FIG. 1 is a sectional view of a phase-locked semiconductor laser array (hereinafter simply referred to as a laser array) showing an embodiment of the present invention.

This laser array has, for example, an n-type GaAs semiconductor substrate 21, and on the semiconductor substrate 21, an n-type Aρx
Ga 1, -x As lower cladding layer 22, n-type AfJ y Ga 1-y As optical waveguide layer 23,
Undoped active layer 24, p-type A-1! y G a
1-y As optical waveguide layer 25, p-type 117Ga1-z
As/GaAs superlattice optical waveguide layer 26, p-type A, I) x
A Gal, As upper cladding layer 27, and a p-type GaAs contact layer 28 are formed in this order. Then, on the lower surface side of the semiconductor substrate 21 and the upper surface side of the contact layer 28,
A n(jlj electrode 29 and a p-side electrode 30 are formed, respectively).

The active layer 24 has a multiple quantum well structure or an AI!
It may be any of the vGa1-vAs layers.

Further, the superlattice leading wave layer 26 has an average composition of AρGa1
The layer thickness ratio between the chapter wall and the well is set so that -w As (y<w<x), and the thickness is, for example, about 0.2 μm. This well width is set so that the refractive index of the superlattice is larger than the average composition at the oscillation wavelength and smaller than the refractive index of the optical waveguide 7!25.

In the superlattice optical waveguide layer 26, a plurality of disordered regions 31 are arranged in a stripe shape.

This disordered region 31 is formed by disordering the superlattice by implanting ions of Si as an impurity, for example. End disordered regions 32 are formed near both ends of the disordered regions 31 arranged in stripes. In this end disordered region 32, Si ions are implanted at a higher concentration than in the disordered region 31 to promote disordering, and its refractive index is set to be smaller than the refractive index of the disordered region 31. ing. By implanting Si ions, the disordered region 31 and the end disordered region 32 become n-type, forming internal current confinement and a refractive index waveguide mechanism.

Next, a method for manufacturing the laser array having the above configuration will be explained using FIGS. 1 and 3(a) and (b). FIGS. 3(a) and 3(b) are process diagrams showing the method for manufacturing the laser array of this example.

First, in FIG. 3(a), an upper cladding layer 22, an optical waveguide layer 23, an active layer 24, an optical waveguide layer 2 are formed on a semiconductor substrate 21.
5 and the superlattice optical waveguide layer 26 are sequentially formed by metal organic vapor phase epitaxy, molecular beam epitaxial growth, or the like. Next, after a SIO7 insulating layer 33 is deposited to a thickness of about 50 nm, the resist layer 34 is patterned into stripes using ordinary photolithography. Thereafter, using the resist layer 4 as a mask, for example, Si ions are injected into the superlattice leading wave layer 26 at an acceleration voltage of about 80 keV at 1×10 14 c.
Ions are implanted to a depth of about m-2. The ion implantation region 35 thus formed is indicated by hatching in the figure.

Next, as shown in FIG. 3(b), a patterned resist layer 36 is formed on the resist layer 34 and the insulating layer 33 using ordinary photorin drying. This resist layer 3
The formation region 6 is the range of the striped resist layer 34, and is not formed near both ends of the stripe. Then,
Using this resist 7136 as a mask, for example, Si ions are heated at an acceleration voltage of about 80 keV at 2 x 1014 cm-
After about 2 implantations, highly accurate ion implantation regions 37 are formed in the superlattice optical waveguide layer 26 near both ends of the stripe.

This ion implantation region 37 is indicated by cross hatching in the figure.

Thereafter, as shown in FIG. 1, the resist layers 34 and 36 and the insulating layer 33 are removed, and the upper cladding layer 27 and the contact layer 28 are sequentially laminated on the superlattice optical waveguide layer 26. Next, heat treatment is performed at about 850° C. for about 30 minutes to disorder the superlattice of the ion implanted region 3537. At this time, the ion implantation region 37 has an average composition AΩw Ga1-
w'', but the shape of the superlattice is slightly preserved in the ion implantation region 35. Subsequently, if an n-side electrode 29 and an n-side electrode 30 are formed on the lower surface side of the semiconductor substrate 21 and the upper surface side of the contact layer 28, respectively, using a vapor deposition method or the like,
A desired laser array is obtained.

The characteristics of the laser array in the above embodiment are shown in FIGS. 4(a), (b) and 5(a).

This will be explained using (b). Figures 4 (a,) and (b) show the lateral distribution of the effective refractive index, where (a) shows the effective refractive index of the laser array of this example and (b) shows the effective refractive index of the conventional laser array. It shows. In addition, Fig. 5 (a>, (b)
) shows the relative gain with respect to the number of supermodes; FIG. The relative gain indicates the gain of the higher-order supermode when the gain of the fundamental supermode is set to 1.

In FIGS. 4(a) and 4(b), the width and spacing of the striped waveguides are W and S, respectively, and the refractive index difference at both ends of the stripe is ΔN. Here, if the refractive index difference between the stripes in FIG. 4(a) in this embodiment is ΔN1, an effective refractive index distribution of ΔN>ΔN1 is realized.

In FIG. 5(a), the number of stripes is 10, W=2
μm, S = 2 μm, and the ratio of ΔN and ΔN1 to the effective refractive index N of the waveguide is ΔN/N = 0.1%, ΔN1/
The relative gain of higher-order supermodes when N=0.05% is shown.

From the figure, it can be seen that in this example, the gain of the fundamental super mode is the largest, and fundamental super mode oscillation is easily obtained. As a result, a unimodal far-field image can be easily obtained.

On the other hand, in a conventional laser array, the effective refractive index distribution is as shown in FIG. 4(b), with 10 stripes and W
The gain of the higher-order supermode in the case of =2 μm, S=2 μm, and ΔN/N−0.1% is as shown in FIG. 5(b). It can be seen from FIG. 5(b) that the gain of the highest order supermode is the largest, and that the highest order supermode oscillation is likely to occur. Therefore, it is difficult to realize a unimodal far-field pattern.

As described above, in this embodiment, the end disordered regions 32 are provided outside the ends of the disordered regions 31 arranged in a stripe shape, and the refractive index of the end disordered regions 32 is set to be lower than the refractive index of the disordered regions 31. By changing the lateral distribution of the effective refractive index, it is possible to obtain fundamental supermode oscillation as shown in FIG. can be easily formed by adjusting the amount of impurity ion implantation and selecting the heat treatment conditions.Therefore, a laser array with fundamental supermode oscillation can be easily obtained, and this can be applied to laser beam printers, satellite communications, YAG lasers, etc. It becomes possible to effectively use it as a light source for excitation of a fiber laser.

Note that the present invention is not limited to the illustrated embodiment, and can be modified in various ways, such as the following modifications.

(1) In Figures 1 and 3 (a>, (b)),
Although the case of the n-type semiconductor substrate 21 is shown, an n-type semiconductor substrate can also be used.

Further, the impurity is not limited to Si ions, and various element ions corresponding to p-type, n-type, etc. can be selected.

(2) Figures 1 and 3 (a>, (b) are AgGa
Although a laser array using an As-based material was shown, instead of this, InGaAsP and InGaAsP using an InP substrate are shown.
AN As-based or InGa using GaAs substrate
The present invention can also be applied to AsP-based laser arrays.

(3) The configuration of the laser array does not need to be limited to that shown in the drawings. For example, the configuration can be arbitrarily changed depending on the use, purpose, etc. of the laser array, such as by providing a buffer layer between the semiconductor substrate 21 and the lower cladding layer 22.

(Effects of the Invention) As described above in detail, according to the present invention, an edge disordered region having a refractive index smaller than the disordered region formed in a stripe shape is formed outside the disordered region. Therefore, by changing the effective refractive index distribution at the laser oscillation wavelength, the gain of the fundamental supermode can be made larger than the gain of other supermodes. Therefore, it is possible to reliably obtain a phase-locked semiconductor laser array that oscillates in the fundamental supermode.

Further, the disordered end region can be easily formed by implanting impurity ions in a larger amount than the disordered region and performing appropriate heat treatment.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a phase-locked semiconductor laser array showing an embodiment of the present invention, FIG. 2 is a cross-sectional view of a conventional phase-locked semiconductor laser array, and FIG. 3(a). (b) is a process diagram showing the manufacturing method of the phase-locked semiconductor laser array shown in FIG. (a) is a distribution diagram according to the present invention, (b) is a distribution diagram according to the conventional method, and FIGS. FIG. 2 is a diagram showing a phase-locked semiconductor laser array of FIG. 21...Semiconductor substrate, 22...Lower cladding layer, 24...Active layer, 26...
Superlattice optical waveguide layer, 27... Upper cladding layer, 3
1...Disordered region, 32... End disordered region.

Claims (1)

[Claims] 1. At least a lower cladding layer, an active layer, a superlattice optical waveguide layer, and an upper cladding layer are sequentially formed on a semiconductor substrate,
In a phase-locked semiconductor laser array in which disordered regions formed by disordering the superlattice are arranged in stripes in the superlattice optical waveguide layer, the disordered regions located at both ends of the stripe are A phase-locked semiconductor laser array characterized in that an edge disordered region having a refractive index smaller than that of the disordered region is formed on the outside. 2. The phase-locked semiconductor laser array according to claim 1, wherein the end disordered region is formed by ion implantation of impurities, and the impurity concentration is higher than that of the disordered region.