JPH067640B2 - Method for manufacturing semiconductor laser device - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor laser device that oscillates in a single axis mode.

(Prior Art) Conventionally, semiconductor lasers having various structures have been proposed as semiconductor laser elements that oscillate in a single axis mode.

Such elements are described in, for example, the literature (Applied Physics Letters), 42 (8).
(1983) P.650-652). FIG. 3 is a schematic view showing this element, which is constructed by arranging the resonators 15 and 17 of the two individual semiconductor lasers 11 and 13 in series at a predetermined interval.

In this element, when a predetermined bias is applied between the individual terminals 19 and 21 of the individual semiconductor lasers 11 and 13 and the common terminal 23 to oscillate these individual lasers, the respective resonators 15 and
The 17 axial modes compete, and only the axial modes with the same wavelength oscillate between the two resonators.However, when the axial modes match at a certain wavelength, other wavelengths up to the wavelengths with the same axial mode match. The intervals are very wide. Therefore, in the wavelength range where the gain of the laser can be obtained, only one axial mode stands (it oscillates only at one wavelength), and therefore, oscillation occurs in the single axial mode.

In the semiconductor laser device having the configuration in which the two resonators 15 and 17 are arranged in series as described above, the two resonators 15 and 17 must be aligned with high accuracy in order to improve the coupling of light.

According to the above-mentioned document, an interval of about 5 μm (dimension shown in FIG. 3 by d) is provided between the two semiconductor lasers 11 and 13 so that the resonators 15 and 17 of these elements are arranged in series on a straight line. (Cu) heat sink aligned with
25 was glued on.

(Problems to be Solved by the Invention) However, since the structure of the conventional semiconductor laser device as described above requires a highly accurate assembly technique, there is a problem that the assembly process of the device is very complicated and difficult. there were.

Therefore, it is not possible to easily provide a semiconductor laser device that oscillates in a single axis mode.

An object of the present invention is to provide a manufacturing method capable of easily manufacturing a semiconductor laser having a structure in which a plurality of resonators are arranged in series on the same underlayer.

(Means for Solving the Problems) In order to achieve this object, according to the method for manufacturing a semiconductor laser device of the present invention, InP (10
A step of forming a semiconductor layer to be a current confinement layer on the (0) plane, and a first groove and a second groove having a depth reaching from the surface of the semiconductor layer to the base layer by etching,
1) a step of forming a first groove having a side surface of A-plane and a second groove orthogonal to the first groove, and the inside of the first groove and the second groove and on the semiconductor layer by a liquid phase epitaxial method. And a step of sequentially forming a lower clad layer, an active layer, and an upper clad layer.

(Operation) According to the manufacturing method of the present invention, the first groove and the second groove orthogonal to the first groove, the lower clad layer, the active layer, and the upper clad layer are formed using the conventional manufacturing technique. Form.

Further, the underlayer is made of InP (100) plane, the first groove is made a groove whose side surface is (111) A plane, and the lower clad layer, the active layer and the upper clad layer are formed by the liquid phase epitaxial growth method. Therefore, the lower cladding layer does not grow in this first groove due to the plane orientation dependence of the liquid phase epitaxial growth. On the other hand, the lower clad layer grows in the second groove orthogonal to the first groove. Also, the active layer grows inside both the first groove and the second groove. Therefore, the height of the active layer in the second groove from the surface of the underlayer is reduced by the layer thickness of the lower clad layer in the intersection area with the first groove, and the discontinuity (step) of the active layer is easy. Is formed. Therefore, resonators are formed in the second grooves on both sides of the first groove.

Embodiments Embodiments of the present invention will be described below with reference to the drawings. It should be noted that these drawings are only schematically shown to the extent that the present invention can be understood, and the shape, size, and arrangement relationship thereof are not limited to the illustrated examples. Further, in these drawings, the same constituent components are designated by the same reference numerals.

FIG. 1 is a perspective view showing the structure of a semiconductor laser device manufactured by the manufacturing method of the present invention.

In FIG. 1, 31 is n-type InP as an InP underlayer.
A substrate (hereinafter, also referred to as a substrate 31) is shown. 33
Indicates, for example, a p-type InP layer as a current confinement layer provided on the (100) surface of the substrate 31 and defined by the first groove 35 and the second groove 37 orthogonal to the first groove. In this embodiment, the first groove 35 has a depth reaching the substrate 31 and is a stripe shape in the <10> direction, and an etchant suitable for forming a groove 35 having a V-shaped cross section orthogonal to this stripe (details will be described later). Is formed by etching. Therefore, the inner side surface of the V groove 35 is the (100) A surface. On the other hand, the stripe-shaped second groove in the <110> direction, which is orthogonal to the first groove (V groove) 35, also has a depth reaching the substrate 31. The cross section of the two grooves 37 orthogonal to the stripe direction has a shogi piece shape (arrow shape toward the substrate 31).

Although the details will be described later, the first groove 35 divides the second groove, and the respective resonators of the two semiconductor lasers are formed in the second groove. Therefore, the width of the first groove 35 is determined according to the design of these two resonators, for example, the degree of coupling of the resonators. The width of the second groove 37 is determined in consideration of the lateral mode control or the like according to the design of the semiconductor laser.

Further, on the inner surfaces of the current confinement layer 33 and the second groove 37, for example, an n-type InP layer 39 as a lower clad layer and, for example, a p-type InGaAsP layer 41 as an active layer (a region shown by diagonal lines in FIG. 1). ) And, for example, p-type InP as the upper clad layer
The cladding layer 43 and the cladding layer 43 are sequentially provided. The active layer 41 inside the second groove 37 is sandwiched by the lower clad layer 39 and the upper clad layer 43 and has a crescent shape. Further, these layers 39, 41 and 43 are buried inside the groove 37 to form a double heterojunction structure and also form a waveguide of laser light in the stripe direction of the groove 37.

On the inner surface of the first groove 35, the p-type InGaAsP active layer 41 and the p-type InP clad layer 43 are provided. Here, the reason why the lower clad layer 39 is not provided inside the first groove 35 is that the active layer provided inside the second groove 37 is formed in the first groove 35.
This is because it is substantially divided by. Although details will be described later, the lower clad layer 39, the active layer 41, and the upper clad layer 43 described above are formed by the liquid phase epitaxial growth to form the first groove 3
5. When grown on the second groove 37 and the current confinement layer 33, InP does not grow in the first groove 35 whose inner surface is the (111) A plane. Therefore, the inner surface of the first groove 35 has a lower cladding layer.
Growth of 39 does not occur, but growth of the active layer 41 follows growth of the lower cladding layer. Therefore, the layer structure inside the first groove 35 and the second groove 37 is different, the height from the surface of the substrate 31 to the active layer provided on the inner surface of the first groove 35, and the surface from the surface of the substrate 31 to the second groove 37.
To the active layer on the inner surface of the lower clad layer
The active layer provided in the first groove 35 becomes lower by the layer thickness of 39. Therefore, since the active layer inside the second groove 37 constitutes a portion (step) that is discontinuously cut in the region of the first groove 35 orthogonal to the second groove 37, the active layer inside the second groove 37 is inside the waveguide. It means that it has been virtually divided.

Further, although not shown, for example, a common electrode is provided on the lower side surface of the substrate 31, and an individual electrode is provided on the upper side of the two resonators 45 and 46 in the region corresponding to the upper side of the groove 37. Configure the element.

In the semiconductor laser device having such a structure, <11
When laser oscillation occurs in the 0> direction, the laser light is partially reflected and partially transmitted in the discontinuous region of the active layer at the intersection region of the first groove 35 and the second groove 37. Because of this, the first groove 35
It is possible to obtain the same effect as forming the first and second resonators 45 and 46 in the grooves of both parts of the second groove 37 divided by, respectively. Therefore, it is as if two resonators are arranged in series. With such a structure, single mode oscillation is possible in the longitudinal mode in which the wavelengths of the two resonators match within the wavelength range in which the gain of the laser is obtained.

According to the manufacturing method of the present invention, the semiconductor laser device described with reference to FIG. 1 can be manufactured by the procedure described below with reference to FIGS. 2 (A) and (B) and FIG.

First, the p-type InP layer 32 is formed as a current confinement layer forming semiconductor layer on the (100) plane of the n-type InP substrate 31 as a base by a liquid phase epitaxial growth method. Then, the second groove 37 is formed in a stripe shape in the <10> direction on the p-type InP semiconductor layer to form the first groove 35 and in the direction orthogonal to the stripe (<110> direction) by a normal photolithography method. Because of the stripe shape, the semiconductor layer 32
Etching mask having a cross-shaped window 51a for exposing
51 (indicated by diagonal lines in FIG. 2 (A)) is formed to obtain the wafer structure shown in FIG. 2 (A). In addition, in FIG. 2 (A),
The dimensions indicated by w ₁ 1 and w ₂ are determined depending on the purpose and design of the first groove and the second groove, as described above.

Next, as a hydrochloric acid-based etchant, for example, an etchant of hydrochloric acid: phosphoric acid = 3: 1 is used, and the semiconductor layer 32 exposed by the window 51a is etched to form the first groove from the surface of the semiconductor layer 32 to the substrate 31. 35 and the second groove 37 are formed at the same time. By this processing, the first groove becomes a groove 35 having a stripe shape in the <10> direction and a cross section orthogonal to the stripe is V-shaped. Therefore, the inner side surface of the V groove 35 is (111) A.
It becomes a face. On the other hand, the second groove that is orthogonal to the first groove 35 has a cross-section that is orthogonal to the stripe direction of the second groove 37 in the shape of a shogi piece (arrow shape toward the substrate 31). In addition, the current confinement layer 33 is formed by the remaining p-type InP semiconductor layer, and the second
A wafer structure shown in FIG.

Next, by liquid phase epitaxial growth method, n-type InP is formed.
A lower clad layer 37, a p-type InGaAsP active layer 41,
The p-type InP upper cladding layer 43 is connected to the first groove 35 and the second groove 37.
And on the current confinement layer 33. In this growth, InP does not grow in the first groove 35 whose inner surface is the (111) A plane. Therefore, the inner surface of the first groove 35 has a lower cladding layer.
39 does not grow, and the p-type InGaAsP layer grows by growing the active layer 41 following the growth of the lower clad layer. On the other hand, on the inner surface of the second groove 37, the lower clad layer 39,
The active layer 41 and the upper clad layer 43 are sequentially grown to form a double heterojunction structure inside the groove. Therefore, it is possible to obtain a semiconductor laser device having a wafer structure as shown in FIG. 1 in which the layer structures inside the first groove 35 and the second groove 37 are different.

In the above-described embodiment, an example in which the underlayer is an n-type InP substrate has been described.
The same effect as that of this embodiment can be obtained even if it is configured with the type InP buffer layer.

The conductivity type of each layer including the substrate may be opposite conductivity type.

Further, in the above-described embodiment, an example in which two resonators are provided on the same underlayer has been described, but the structure and manufacturing method of the present invention form a plurality of (three or more) resonators on the same underlayer. It is also suitable for use when

Furthermore, the position of the first groove dividing the second groove is not limited to the center of the length of the second groove in the stripe direction,
The optimum position can be set according to the purpose and design.

(Effect of the Invention) As is clear from the above description, according to the method for manufacturing a semiconductor laser of the present invention, two resonators are integrated by using the photolithography technology and the plane orientation dependence of liquid phase epitaxial growth. It can be accurately formed on two substrates.
Therefore, the high-precision assembly technique used conventionally is unnecessary.

Therefore, it is possible to provide a method for easily manufacturing a semiconductor laser having a structure in which a plurality of resonators are arranged in series on the same underlayer.

[Brief description of drawings]

FIG. 1 is a perspective view showing the structure of a semiconductor laser device of the present invention, FIGS. 2 (A) and 2 (B) are manufacturing process diagrams showing an example of a method for manufacturing a semiconductor laser of the present invention, and FIG. It is a diagram for explaining. 31 ... Underlayer (n-type InP substrate) 32 ... Semiconductor layer for forming current confinement layer (p-type InP layer) 33 ... P-type InP current confinement layer 35 ... First groove, 37 ... Second groove 39 ... Under n-type InP Side clad layer 41 ... P-type InGaAsp active layer 43 ... P-type InP upper clad layer 45 ... First resonator, 47 ... Second resonator 51 ... Etching mask, 51a ... Window.

Claims (1)

[Claims] 1. A step of forming a semiconductor layer to be a current confinement layer on a (100) plane of InP as an underlayer, and a first groove having a depth reaching from the surface of the semiconductor layer to the underlayer by etching. A second groove, (111)
A step of forming a first groove having a side surface of A surface and a second groove orthogonal to the first groove; and a step of forming a second groove in the first groove and the second groove and on the semiconductor layer by a liquid phase epitaxial method. And a step of sequentially forming a side clad layer, an active layer and an upper clad layer.