JPS63307792A - Semiconductor laser array element and manufacture thereof - Google Patents

Abstract

PURPOSE:To oscillate all the semiconductor lasers of an array in a state of phase lock by forming at least one irregular sections adjacent to both sides of an irregular section constituting an optional guide. CONSTITUTION:A semiconductor laser array element is composed of a plurality of optical guides shaped in response to irregularities 4 formed onto a substrate 1, and at least one irregular sections 5 are shaped adjacent to both sides of the irregular section 4 forming the optical guides. That is, a uniform flat active layer 7 can be formed extending over the whole regions of active regions in semiconductor laser array elements by juxtaposing the irregular sections 5 on the substrate 1 side at positions adjacent to the active regions consisting of a plurality of the optical guides. Accordingly, laser oscillation in a state of phase lock is acquired.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to the structure and manufacturing method of a semiconductor laser array element.

<Prior art and its problems> Research is progressing on semiconductor laser arrays that increase output by arranging a plurality of semiconductor lasers close to each other on the same substrate. In these devices, a double heterojunction structure is often formed by liquid phase epitaxial growth on an uneven substrate to form a limited region as an active region by controlling light or current, and various structures have been realized.

However, when performing multilayer liquid-phase epitaxial growth on a substrate with multiple stripes of unevenness, a phenomenon occurs in which the thickness of the grown layer on the unevenness at the periphery differs from that on the unevenness near the center. As a result, a uniform growth layer cannot be obtained. As an example, FIG. 6(a) shows a cross section of a wafer after liquid phase epitaxial growth, and FIG. 6(b) shows a plan view of the unevenness formed on the substrate.

Kn-type GaAs (or Ga
AtAs) current confinement layer (62) is formed by liquid phase epitaxial method, nine molecular beam epitaxial growth method, organometallic chemical deposition method, or the like.

Thereafter, using photolithography and etching techniques, a plurality of striped groove-shaped recesses (63) are carved from the surface, penetrating the n-type caAs (or GaAtAs) current confinement layer (62) and reaching the substrate (61). Set up Next, using this as a substrate, p-type Ga1-)(AtxAs cladding layer (641), p (or n)-type Ga1-yAtyAs active layer (65), n-type Ga1, (AtxA 4322
21 layers (6(2), n+ type GaAs cap layer (6η) are continuously grown by liquid phase epitaxial growth (where o<y<x<I).

At this time, the layer thickness of the p-type Ga 1-X AtX As cladding layer (64I) is thicker in the concave portions (63) and thinner in the flat portions due to the difference in growth rate depending on the plane orientation of the substrate (69). ) p-type Ga 1-X Atz As cladding layer on the concave part (63) near the flat part of
The layer thickness of 4) is the same as that of the concave part (63
) The layer thickness of the p-type rad layer '6 (1) on the flat part is made thinner to 0.1 to 0.5 μm to form the concave part. If an optical waveguide is to be formed on (63), the surface of the p-type cladding layer ('64) and the active layer ((to)) will be curved, as shown in FIG. 6(b).

As a result, the propagation constant of each waveguide is different, so
Phase-locked oscillation cannot be obtained, and each waveguide oscillates at its own oscillation threshold and oscillation wavelength.

<Object of the Invention> In view of the above-mentioned problems, the present invention provides a semiconductor laser array element in which a plurality of semiconductor lasers are arranged close to each other on the same substrate, in which all the semiconductor lasers oscillate in a phase-locked state. The object of the present invention is to provide a laser array element.

<Means for Solving the Problems> The present invention provides a semiconductor laser array composed of a plurality of optical waveguides formed in correspondence with the unevenness by providing unevenness on a substrate for centralized control of light and current. In the element, at least one
This feature is characterized by the formation of individual uneven portions.

Effect> The semiconductor laser array element of the present invention is constituted by a plurality of optical waveguides for laser oscillation, and uneven portions are arranged in parallel on the substrate side at positions close to the active region made up of the plurality of optical waveguides. As a result, a uniform and flat active layer can be formed over the entire active region of the semiconductor laser array element, making it possible to obtain laser oscillation in a phase-locked state.

<Embodiment> FIG. 1 is a configuration diagram of a semiconductor laser array element showing one embodiment of the present invention, FIG. 1(a) is a cross-sectional view, and FIG.
) is a plan view showing the uneven structure (current injection region and optical waveguide) formed on the substrate. In this example, GaAtAs
A case where the present invention is applied to a semiconductor laser array element will be described.

Liquid phase epitaxial (LP) is deposited on the p-type GaAs substrate (1).
A 1 μm thick n-type GaAs (or GaAtAS or multilayer structure of GaAs and GaAtAs) current blocking layer (2) having opposite polarity is grown by a crystal growth method such as method E).

Next, using photolithography and etching techniques, recesses (3) with a width of 4 μm and a pitch of 5 μm are formed in the striped groove shape shown in FIG.
1) Form to a depth that reaches inside. Formation of a recess (3) - whereby the removed portion of the current blocking layer (2) on the substrate (1) becomes a current path and an optical waveguide. Here, the plurality of uneven parts (4) in the center become the light emitting area of the phase-locked laser array device, and the uneven parts (5) formed at a distance of 6 μm from the light emitting area of the laser array on both sides are active areas of the laser array device. It is used to form layer (7) flat and uniform. At this time, the uneven parts formed on both sides (
5) does not necessarily have to have the same shape and the same period as the unevenness (4) in the center. That is, 0.2.4 m above the convex portion is placed on the substrate (1) on which the concave and convex portion is formed using the LPE method again.
Thick p-type Ga 1-X ALxA s cladding layer (6
), 0.08 μm thick p-type (or n-type) Ga1-
y AA, As (or quantum well structure stacked with GaAs and GaAAAs) active layer (7), 1 μm thick n-type Ga1
A double heterojunction multilayer crystal structure for laser oscillation is constructed by continuously growing an As cladding layer (8) and a 2 μm thick n+ type GaAs cap layer (9). y<x<I). At this time, since uneven portions (5) are formed on both sides close to a position 6 μm away from the semiconductor laser array portion, uneven diffusion of As in the Ga solution does not occur and the n-cladding layer (6) When the active layer (7) is sequentially grown, a flat and uniform active layer (7) can be grown in the laser array section (4) and its vicinity.

Next, a resist film is formed on the semiconductor laser array section (4) using photolithography to serve as a protective film, and then protons are injected using the ion implantation method to increase the resistance of the crystals other than the semiconductor laser array section. get the results. As a result, current flows through the semiconductor laser array section (4), but even though current paths are formed on both sides, optical coupling and current injection are difficult due to the distance of 6 μm from the laser array section. This results in a structure that does not occur.

After producing the current stripe structure, a p-side resistive electrode 00 is formed on the substrate (1) side, and an n-side resistive electrode αD is formed on the growth layer side, that is, on the cap layer (9), so that the resonator length is 200~ It is interosseous at right angles to the recess (3) so that the distance is aOOμm.

Next, attach At203 film or amorphous S to the opening surface of both valves.
The i film is coated by electron beam evaporation to form a laser surface mirror. At this time, the reflectance of the reflective film is arbitrarily set from about 2% to 95% by appropriately changing the thickness of each layer in the reflective film composed of a single-layer At203 film or a multilayer At203 film and an amorphous Si film. be able to.

In order to obtain high output light, an At203 film with a thickness of λ/4 (λ: oscillation wavelength) is formed on the interosseous surface on the laser beam output side.
A multilayer film of an Az2O3 film and a Si film is formed on the back interosseous surface by electron beam evaporation to form a laser mirror with a reflectance of about 2% and about 95%, respectively.

As a result, the semiconductor laser array element of this example had an oscillation threshold of 100 mA and oscillated in a stable phase-locked state with a bimodal far-field pattern up to an optical output of 200 mW.

As described above, by forming unevenness on both sides of the laser array part, a flat and uniform active layer (7) can be manufactured, and current and light can be effectively confined in the laser array part (4). It becomes possible to cause laser oscillation in a phase synchronized state over the entire area of the laser array section (4).

Note that the method for confining the injection current only to the semiconductor laser array portion is not limited to the proton injection method, and other methods may be used. Further, the waveguide structure (concave-convex structure) of the semiconductor laser array section may not only have a parallel stripe shape but also have other shapes, and the concave-convex structure on both sides does not need to be limited to the parallel shape.

FIG. 2 is a configuration diagram of a semiconductor laser array element showing a second embodiment of the present invention, FIG. 2(a) is a sectional view, and FIG. , Figure 2(c)
shows a modified embodiment of FIG. 2(b).

In this example, the injection current is set to n-type Ga (1 gAtO, lA
A convex p-type GaAs substrate is used so that the current blocking layer of s12υ and n-type GaA, s(A) can be limited to the light emission range of the laser array.

Furthermore, the waveguide structure of the semiconductor laser array is shown in Figure 2 (b).
) Alternatively, as shown in FIG. 2(c), there is a laser array waveguide structure in which optical waveguides shifted by half a pitch are smoothly joined using branched waveguides.

FIG. 3 is a configuration diagram of a semiconductor laser array element showing a third embodiment of the present invention, FIG. 3(a) is a cross-sectional structural diagram of the laser array, and FIG. 3(b) is a concavo-convex structure on a substrate. FIG. 3(C) is a plan structural view showing a modified embodiment of the aql(b).

The waveguide structure of the laser array is such that semiconductor lasers parallel to each other are smoothly coupled using a branching waveguide near the end face.

In addition, the current confinement structure (strive structure) to the light emitting region of the laser array is
After removing a part of the aAs cap layer (9) and the n-GaA/As cladding layer (8) by etching, a barrier film G1) such as a SiN film is formed to restrict the downstream side.

Other structures include an n-GaAs cap layer (9) outside the light emitting region, an n-Ga, AtAs cladding layer (8),
Active 'M (7).

p-GaAlAs clad 9 (6), Ga
A, s It is possible to narrow the π flow to the entire optical region of the laser array even if the substrate m, etc. is removed by etching and the downstream is restricted by similarly inducing insulation. In this case, the uneven portions on both sides may eventually be removed.

FIG. 4 is a configuration diagram of a semiconductor laser array element showing another embodiment of the present invention.

The current confinement structure is an n-GaAs cap layer (9).
In this method, selective diffusion technology is used to diffuse Zn into regions other than the light emitting region of the laser array to form p-type GaAs Qυ, thereby performing current confinement using a pn junction.

FIG. 5 is a cross-sectional configuration diagram of a semiconductor laser array element showing a fifth embodiment of the present invention.

After the multilayer structure shown in FIG. 5(a) is formed by epitaxial growth, the multilayer structure on both sides is removed by chemical etching until it reaches the GaAs substrate (1), leaving the semiconductor laser array section (4). Thereafter, by selective epitaxial growth, n −
A GaAtAs buried layer (511, high resistance GaAtAs layer: 52) and a p-GaAtAs buried layer (53) are sequentially grown to perform current confinement. In this case, the recesses (5) on both sides will eventually be completely removed.

In each of the above embodiments, an n-type substrate is used, but even when an n-type substrate is used and the conductivity types of each layer are reversed, the present invention provides exactly the same effect.

Furthermore, in addition to GaAtAs-based semiconductor laser arrays, other semiconductor laser arrays with uneven substrates, such as I
Similar effects can be brought about in nGaAsP-I n P medium conductor laser arrays.

<Effects of the Invention> As described above, in a semiconductor laser array element constituted by an optical waveguide formed by providing a plurality of irregularities on a substrate for controlling light and current, each light emitting region of the laser array By forming at least one concavity or convexity on both sides of the concavity and convexity forming the active layer, the active layer can be crystal-grown to a flat shape with a uniform layer thickness, and also current and light can be applied to the light emitting region. can be effectively confined, so each laser emission region has the same oscillation wavelength.
Laser oscillation occurs at the oscillation threshold, and laser oscillation can be performed in a phase-locked state over the entire light emitting region.

[Brief explanation of drawings]

FIG. 1(a) is a sectional view of a semiconductor laser array according to a first embodiment of the present invention, and FIG. 1(b) is a plan view of an uneven structure formed on the substrate thereof. FIG. 2(a) is a cross-sectional view of a semiconductor laser array according to a second embodiment of the present invention, and FIG. 2(b) is a plan view of an uneven structure formed on the substrate. (C) is a plan view of another uneven structure. FIG. 3(a) is a cross-sectional view of a semiconductor laser array according to a third embodiment of the present invention, and FIG. 3(b) is a plan view of an uneven structure formed on the substrate. (c) is a plan view of another uneven structure. FIG. 4 shows a cross-sectional view of a semiconductor laser array according to a fourth embodiment of the present invention. FIG. 5(a) is a sectional view of a semiconductor laser array according to a fifth embodiment of the present invention, and FIG. 5(b) is a plan view of the structure. FIG. 6(a) is a cross-sectional structural diagram of a conventional semiconductor laser array device, and FIG. 6(b) is a plan view showing an uneven structure formed on the substrate thereof. 1 ・-p-GaAs substrate 2- n-GaAs or n
-GaAtAs current blocking layer 3... recess 4... light emitting region 6-p - GaAtA, s cladding layer 7-p
(or n)-GaAs (or GaAtAs) active layer
8-n-GaAtAs cladding layer 9...n-
GaAs cap layer 10...p side electrode 1t-=n
Side electrode 2 + -n-GaAtAs current blocking layer 2
2...n-GaAs current blocking layer 23...p-G
aAs substrate 31...Insulating film 51.53...Buried layer 52...High resistance layer Agent Patent attorney Takeshi Sugiyama (and 1 other person) (a) (b) Figure 1 (a) (b) )

Claims (1)

[Scope of Claims] 1. In a semiconductor laser array element constituted by a plurality of optical waveguides formed corresponding to the unevenness provided on a substrate, the semiconductor laser array element is provided with a plurality of optical waveguides adjacent to both sides of the unevenness forming the optical waveguide. 1. A semiconductor laser array element characterized in that at least one concave portion or convex portion is formed. 2. Forming a concavo-convex portion for forming an optical waveguide for laser oscillation on a semiconductor substrate and at least one concave portion or convex portion close to both sides of the concave-convex portion, and an active layer forming the optical waveguide on the substrate. 1. A method for manufacturing a semiconductor laser array element, comprising the step of growing a double heterojunction structure.