JPS62171179A - Semiconductor laser element and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture a semiconductor laser element, which has internal stripes having uniform stripe width of 1mum or less and excellent flatness and oscillates at low threshold currents and in which fine spot oscillation is acquired, by forming double hetero-junction structure on the upper side of the flat end surface of a laminate including a channel layer. CONSTITUTION:A P-type AlxGa1-xAs layer 33 as a channel layer and an N-type GaAs layer 35 as a second layer are shaped onto a substrate 31 in succession. A flat end surface 37a acquired by cleaving these semiconductor layers 31, 33 and 35 is formed in the direction orthogonal to the lamination planes of a laminate 37 constituted of a first layer, the channel layer and the second layer. Double hetero-junction structure 45 is shaped on the upper sides of the flat end surface (a cleavage plane) 37a and the N-type GaAs layer 35 directly or indirectly. The width of stripes for confining carriers and beams in the direction parallel with the joint surfaces of the double hetero-juntion 45 can be specified by the layer thickness (size shown by t) of the channel layer 33. The stripes are shaped in the direction vertical to a paper surface, and a section S represents the section of an active layer section orthogonal to the direction of the stripes.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor laser device that oscillates in a single longitudinal mode and at a minute spot, and a method for manufacturing the same.

(Prior art) Figures 4(A) to 4(C) are based on, for example, the literature (Applied Physics Letters).
Letters) 46 (1985) P, 102
3 to 1025) are manufacturing process diagrams for explaining the structure and manufacturing method of the conventional internal stripe type semiconductor laser device disclosed in Nos. 3 to 1025). Since this element has a structure effective for transverse mode oscillation control, it can oscillate at a minute spot.

First, the n-type G is grown by -th liquid phase epitaxial growth.
On the aAs substrate 11, an N-type AnXGa, -XAs first cladding layer 13 and a p-type AjZ, Ga, -.

As active layer 15, P-type AJ2. A Ga, -XAs second cladding lower layer 17 and an n-type GaAs semiconductor layer 19 serving as a current confinement layer are successively formed, as shown in FIG. 4(A).
A wafer structure as shown in is obtained.

Next, after masking the necessary portions of the n-type GaAs semiconductor layer 19 by normal photolithography, furthermore, the n-type GaAs semiconductor layer 19 other than this portion is masked by a p-type AflXG.
a. A partial region of this n-type GaAs semiconductor layer 19 is etched so as to remain on the As second cladding lower layer 17 with a layer thickness of approximately 1 μm, and an inverted mesa portion 19a is formed in a part of this semiconductor layer 19. do.

Next, by a second liquid phase epitaxial growth, N
A type Aλ, lGap-XAs current confinement layer 21 is formed on the n-type GaAs semiconductor layer 19 except for this inverted mesa portion 19 to obtain a wafer structure as shown in FIG. 4(B).

Next, the entire surface of the wafer is melted back with an unsaturated GaAs meltback melt. During this meltback, the meltback speed of GaAs is AJ2XGa, -, A
The exposed n-type Ga
Only the reverse mesa portion 19a of the As semiconductor layer is selectively melt-etched down to the second cladding lower layer 17 to form an internal stripe, so that the n-type GaAs semiconductor layer 19 becomes a current confinement layer. Following this, P-type l
An XGa, -XAs layer is grown inside the stripe and on the current confinement layer to form a current confinement channel part 23a of the second cladding layer and a second cladding upper layer 23b, and the p-type GaAs layer is roughly grown. 25 is grown on the second cladding upper layer 23b to form a cap layer 25.

As described above, the first cladding layer 13, the active layer 15, the second cladding lower layer 17, the current confinement channel part 23a, and the second cladding upper layer 23b are formed on the base, and therein is an n-type layer. GaAs layer and N-type AM, G
An internal stripe type semiconductor laser device as shown in FIG. 4(C) was obtained, which was provided with a second cladding layer 27 having an internal current confinement layer composed of a I-x As. Such a semiconductor laser element stably oscillates in a single transverse mode and emits a minute spot.

(Problem to be Solved by the Invention) However, in the internal stripe type semiconductor laser device as described above, the width of the stripe has to be narrowed due to processing limitations of photo-etching technology, such as the exposure limit of a photomask. Since the limit of what can be achieved is determined, there is a problem in that it is difficult to obtain a semiconductor laser device with a stripe width of 1 μm or less and which oscillates with a smaller spot.

Furthermore, since the stripes are formed by an etching process, it is difficult to make the stripe width uniform at various locations in the stripe direction within the device. Furthermore, since the stripes are formed on the surface of the substrate processed by lapping or the like, there is a problem in that the flatness of the stripes depends on the flatness of the substrate. Such a problem impairs the linearity of the stripe and deteriorates the characteristics of the semiconductor laser device.

The object of the first invention of this application is to solve the above-mentioned problems, to provide an internal stripe with a uniform stripe width of 1 μm or less and good flatness, to oscillate with a low threshold current, and to oscillate with a minute spot oscillation. An object of the present invention is to provide a semiconductor laser device that can obtain the following properties.

The object of the second invention of this application is to provide a semiconductor laser device which has an internal stripe having a uniform stripe width of 1 μm or less and good flatness, which oscillates with a low threshold current, and which can achieve minute spot oscillation. An object of the present invention is to provide a manufacturing method that can easily manufacture.

(Means for solving the problem) In order to achieve this object, according to the present invention, at least a first layer, a channel layer connected to one electrode,
a second layer, a double heterojunction structure laminated on the upper side of the flat end surface of this laminate, and a layer directly or indirectly provided on the opposite side of the double heterojunction structure from the above-mentioned end surface. It is characterized by comprising the other electrode.

In carrying out this invention, the first layer is a first conductivity type semiconductor layer, the channel layer is a second conductivity type semiconductor layer, and the second layer is a first conductivity type semiconductor layer, and a laminate including these semiconductor layers is formed. It is preferable to configure.

In carrying out the present invention, it is preferable that the flat end face of the laminate be used as the cleavage plane of the semiconductor layer.

Furthermore, in manufacturing a semiconductor laser device having an internal stripe having a uniform stripe width of less than Il, tm and good flatness, the manufacturing process involves forming a first layer, a channel layer, and a second layer. forming a laminate having sequentially;
A step of forming a flat end surface on this laminate, a step of forming a double heterojunction structure directly or indirectly on the upper side of this end surface, a step of forming one electrode on the channel layer described above, and a step of forming a double heterojunction structure on the above-mentioned channel layer. The method is characterized in that it includes a step of forming the other electrode in the heterojunction structure.

In implementing the manufacturing method of the present invention, the first layer is a first conductivity type semiconductor layer, the channel layer is a second conductivity type semiconductor layer,
Preferably, the second layer is a first conductivity type semiconductor layer, and a laminate including these semiconductor layers is formed.

In carrying out the manufacturing method of the present invention, it is preferable to form a flat end face by cleaving the semiconductor layer.

(Function) According to the structure of the semiconductor laser device of the present invention, the double heterojunction structure is provided above the flat end surface of the laminate including the channel layer. Therefore, a partial region of the double heterojunction structure corresponding to the end face of this channel layer becomes a stripe of the semiconductor laser device. Further, the width of the stripe is determined by the layer thickness of the channel layer, and the flatness of the stripe is determined by the flatness of the end face.

By the way, for example, if the first layer is a first conductivity type semiconductor layer, the channel layer is a second conductivity type semiconductor layer, and the second layer is a first conductivity type semiconductor layer, the cleavage plane perpendicular to the lamination plane of these semiconductor layers is When a double heterojunction structure is provided on the upper side, since the cleavage plane is an extremely flat surface, stripes with good flatness can be easily obtained.

Further, according to the manufacturing method of the present invention, the manufacturing process includes a step of forming a laminate having a first layer, a channel layer, and a second layer in this order. Since the formation of each of these layers and the control of layer thickness etc. can be easily performed with high accuracy using conventional techniques, it is possible to easily form a channel layer having an arbitrary and uniform layer thickness of, for example, 14 m or less. Therefore, when a double heterojunction structure is formed on a flat end surface of a laminate including this channel layer, the double heterojunction partial region corresponding to the end surface of this channel layer has an arbitrary and uniform width.
In addition, it becomes a stripe of a flat semiconductor laser element.

Note that, for example, when the first layer is a first conductivity type semiconductor layer, the channel layer is a second conductivity type semiconductor layer, and the second layer is a first conductivity type semiconductor layer, the direction perpendicular to the lamination plane of these semiconductor layers. A flat end face can be easily obtained by forming a cleavage plane of the semiconductor layer.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that these figures are merely schematic illustrations to facilitate understanding of the present invention, and the shapes, dimensions, and arrangement relationships are not limited to the illustrated examples. Further, in these figures, the same components are designated by the same reference numerals.

In this case, the first layer is, for example, an n-type GaAs substrate as a first conductivity type semiconductor layer, the channel layer is, for example, a p-type AJZXGa, □As layer as a second conductivity type semiconductor layer, and the second layer is, for example, a first conductivity type semiconductor layer. n-type GaAs as a conductive semiconductor layer
This will be explained using an example of layers.

FIG. 1 is a sectional view showing the structure of a semiconductor laser device of the present invention. In FIG. 1, numeral 31 indicates an n-type GaAs substrate (hereinafter sometimes referred to as a substrate) as a first layer.

On this substrate 31, a P-type AIL as a channel layer,
n-type GaAs as the third second layer on the Ga, -XAsAs layer
The layers 35 are sequentially provided. Further, it has a flat end face 37a obtained by cleaving these semiconductor layers 31, 33, and 35 in a direction perpendicular to the stacked surface of the stacked body 37 composed of the first layer, the channel layer, and the second layer. There is. Also, for example, P-type AjZ, Ga, -, A as the lower cladding layer.
s layer 39 and A2□0 a l-z A as an active layer
s layer 41 and N-type AJZ and G as upper cladding layers.
A double heterojunction structure 45 composed of a, -, As layers 43 is formed with a flat end face (cleavage plane) 37a and an n-type GaAs layer 43.
It is provided directly or indirectly above the layer 35. Note that the double heterostructure may be provided at least above the flat end surface 37a.

Further, a predetermined region of the channel layer 33 is exposed, and one electrode 47 is connected to the exposed portion, and the other electrode 47 is directly or indirectly connected to the side opposite to the aforementioned end surface 37a of the double heterojunction structure 45. The semiconductor laser device of the present invention is configured by providing the electrode 49.

In this semiconductor laser device, the thickness of the channel layer 33 (dimension indicated by t in FIG. 1) defines the width of the stripe for confining carriers and light in the direction parallel to the junction surface of the double heterojunction 45. You can. That is, the stripes are provided in a direction perpendicular to the paper plane of FIG. 1, and the shaded portion S in FIG. 1 is a cross section of the active layer portion perpendicular to the stripe direction. Also, the stripes will be provided on a flat cleavage plane.

Therefore, it is possible to obtain stripes of a semiconductor laser device in which the width of the stripes is very narrow, arbitrary and constant, and furthermore, has excellent linearity. Therefore, oscillation occurs at an extremely small spot.

Furthermore, since the second and second layers made of n-type GaAs sandwiching the channel layer 33 act as current confinement layers, oscillation occurs at a low threshold current, and the second and second layers are effective for transverse mode control. It also acts as a light absorption layer.

Hereinafter, a method for manufacturing a semiconductor laser device according to the present invention will be explained with reference to FIGS. 2(A) and 2(B) and FIG. 1.

First, by a suitable method such as molecular beam epitaxial growth, P-type fiX Ga,
- Three n-type GaAs layers 35 are sequentially formed on the XAsAs layer to obtain a laminate 35. Subsequently, this laminate 37 is cleaved in a direction perpendicular to the laminate plane to form a cleavage plane 37a,
A wafer structure as shown in FIG. 2(A) is obtained.

Next, by the second epitaxial growth, P-type AnyGa, -,
As layer 39 and Al1. Ga, -.

An As layer 41 and an N-type Al, Ga, -, As layer 43 are sequentially formed to form a double heterojunction structure 45, thereby obtaining a wafer structure as shown in FIG. 2(B).

Next, in a region spaced apart from the cleavage plane 37a and on the laminated surface of the laminated body 37, an N-type Al, Ga, -, As layer 43,
Hel□Ga, As layer 41% P type An.

Parts of the Ga, -yAs layer 39 and the n-type GaAs layer 35 are removed to expose a part of the channel layer 33. Subsequently, one electrode 47 is formed above the exposed channel layer 330 portion. Further, by forming the other electrode 49 on the side opposite to the aforementioned end surface 37a of the double heterojunction structure 45, the semiconductor laser device of the present invention as shown in FIG. 1 can be obtained.

Although the above-mentioned embodiment has been described using an n-type GaAs substrate, a p-type GaAs substrate may be used and the conductivity type of each layer may be the opposite conductivity type to that of the embodiment.

Further, the semiconductor laser device of the present invention is not limited to the above-described embodiments, and the materials used, the method of forming the laminate, and the method of forming the flat end face may be other suitable materials and forming methods.

For example, a semiconductor laser device can be constructed using an InP-based material. Further, the first layer and the second layer are composed of an insulating layer such as Sio2, the channel layer is composed of a metal thin film layer formed by, for example, a vacuum evaporation method, and a laminated layer consisting of SiO□ and a metal thin film layer is formed. A semiconductor laser device may be manufactured in which a flat end face is formed on the body and a double heterojunction structure is provided at least above the end face.

In this case, the stripe width of the semiconductor laser is determined by the thickness and precision of the metal thin film formed by vacuum evaporation.

Further, as shown in FIG. 3, the first layer 31, the channel layer 33, and the second layer 35 are sequentially provided on the base 51, and each layer 35 is formed from the surface of the second layer 35 to the base 51 by etching, for example. .33 and 31 may be partially removed to form a flat end face 53, and the semiconductor laser element may have a double heterojunction structure 45 above this end face 53.

Note that the first layer, channel layer, second layer, and each layer constituting the double heterojunction structure may be formed by other suitable methods such as liquid phase epitaxial growth, metal organic pyrolysis vapor deposition (MOCVD), etc. May be used.

(Effects of the Invention) As is clear from the above explanation, according to the semiconductor laser device and the manufacturing method thereof of the present invention, the double heterojunction structure has a flat end face of the stack including the channel layer (for example, the opening of the crystal). provided on the upper side of the surface). Therefore, the partial region of the double heterojunction structure corresponding to the end face of the channel layer becomes a stripe of the semiconductor laser device. Further, the width of the stripe is determined by the layer thickness of the channel layer, and the flatness of the stripe is determined by the flatness of the end face.

By the way, it is easy to set the thickness of this channel layer to an arbitrary and uniform layer thickness of 1 μm or less, for example, and to form a flat end face using conventional film forming techniques and processing techniques. Therefore, it is possible to provide a semiconductor laser device having a uniform stripe width of 1 μm or less and a good internal stripe with a stripe flatness of about one atomic layer throughout the laser cavity, and a method for manufacturing the same.

Therefore, it is possible to provide a semiconductor laser device that oscillates with a low threshold current and oscillates in a smaller spot than the conventional one.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the structure of a semiconductor laser device of the present invention, FIGS. 2(A) and (B) are manufacturing process diagrams for explaining the manufacturing method of the present invention, and FIG. 3 is a cross-sectional view showing the structure of a semiconductor laser device of this invention. FIGS. 4A to 4C are diagrams illustrating a conventional semiconductor laser device. 31... First layer (n-type GaAs substrate) 33-... Channel layer (P-type AlXGa, -xAs layer) 35-... Second layer (n-type GaAs layer) 37-... Laminated body 37a...・Flat end surface (opening surface of laminate) 39...
Lower cladding layer 41...active layer 43...upper cladding layer 45...double heterojunction structure 47...one electrode, 49...other electrode 51
- Base 53 - A flat end surface formed by etching. Patent applicant Oki Electric Industry Co., Ltd. Jf No.-k
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Claims (6)

[Claims] (1) A laminate consisting of at least a first layer, a channel layer connected to one electrode, and a second layer, a double heterojunction structure laminated above the flat end surface of the laminate, and the double heterojunction structure A semiconductor laser element comprising another electrode provided on a side opposite to the end surface of the bonding structure. (2) Claim 1, characterized in that the first layer is a first conductivity type semiconductor layer, the channel layer is a second conductivity type semiconductor layer, and the second layer is a first conductivity type semiconductor layer. The semiconductor laser device described above. (3) The semiconductor laser device according to claim 2, wherein the flat end face is the cleavage plane of the semiconductor layer. (4) forming a laminate having a first layer, a channel layer, and a second layer sequentially; forming a flat end face on the laminate; and forming a double heterojunction structure on the upper side of the end face. A method for manufacturing a semiconductor laser device, comprising the steps of: forming one electrode on the channel layer; and forming the other electrode on the double heterojunction structure. (5) Claim 4, characterized in that the first layer is a first conductivity type semiconductor layer, the channel layer is a second conductivity type semiconductor layer, and the second layer is a first conductivity type semiconductor layer. A method of manufacturing the semiconductor laser device described above. (6) The method for manufacturing a semiconductor laser device according to claim 5, wherein the flat end face is formed by cleaving the semiconductor layer.