JPS601883A - Semiconductor laser device and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a self-matching type semiconductor laser having excellent lateral mode control with a vapor phase growing method (MOCVD method) using organic metal by inclining the planar azimuth of the surface of a ground substrate having a striped groove from (100) surface. CONSTITUTION:A current narrowing layer 2 is epitaxially grown by an MO CVD method on a substrate 1 having the planar azimuth inclined at 2 degree in (011) direction from (100) surface, and selectively etched to form a striped groove 2a in (011) direction. A clad layer 3, an active layer 4, a clad layer 5 and a contacting layer 6 are sequentially grown by the MOCVD method. Stepwise difference is formed on the top of the groove 2a in the layer 4, and the thickness is largely increased. Accordingly, light enclosing effect increases, stable lateral mode control can be performed. The lateral mode control structure and the current narrowing structure can be performed in one step simultaneously, thereby largely simplifying the manufacturing steps.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to improvements in a semiconductor laser device and its manufacturing method.

[Technical background of the invention and its problems]

In recent years, individual semiconductor lasers have come to be used in floor desks as light sources for optical communications and as optical sources for optical discs. Semiconductor lasers for such applications require control of the transverse mode as well as a structure that can be produced at low cost and has excellent mass productivity. A so-called self-aligned semiconductor laser is known as a half-branched L-body laser having a structure excellent in transverse mode control and mass productivity. Since this laser can simultaneously achieve transverse mode control and current confinement to the light emitting region in one process, it has a small number of manufacturing processes and is extremely advantageous in terms of reducing the cost.

On the other hand, I1↑Met
al-Organic Chemical Vapor
The deposition method (hereinafter abbreviated as MOCVD method) is attracting attention as a manufacturing method for semiconductor lasers with excellent mass productivity because it allows the growth of a homogeneous thin film crystal over a large area. However, the MOCVI) method is different from the conventional liquid phase epitaxy (T, 1qld Phase Ep
Since the crystal growth mechanism is different from that of the ltaxy method (hereinafter abbreviated as LPFi method), it may be difficult to realize the transverse mode control structure of a semiconductor laser that has been made using the LPE method using the MOCVD method.

Therefore, it is desired to develop a semiconductor laser having a transverse mode control structure that meets the characteristics of the MOCvD method.

[Purpose of the invention]

The object of the present invention is to achieve the following:
An object of the present invention is to provide a self-aligned semiconductor laser device that is excellent in mass production and a method for manufacturing the same.

[Summary of the invention]

The gist of the present invention is to form a double heterojunction structure by MOCVD on a substrate having stripe-shaped grooves and having a plane orientation perpendicular to the grooves and tilted from (100). .

The present inventors have conducted various experiments for crystal growth on the grooves.
As a result of overlapping, by tilting the plane orientation of the surface of the base substrate from (100), a step is created in the crystal layer formed on the top of the groove, for example, the active layer, and in that part there is a layer that is necessary for stable transverse mode control. It was found that a sufficient increase in film thickness occurred to cause a refractive index difference. Further, according to further intensive research by the inventors, the above-mentioned step difference and film thickness increase phenomenon occurring in the active layer vary depending on the inclination of the plane orientation of the substrate surface from the (100) plane, the crystal growth conditions, etc. found. Therefore, using the above method, the plane orientation of the substrate surface and the crystal growth line f(
If etc. are selected appropriately, not only the LIjE method but also the MOC
The VD method also makes it possible to realize the self-aligned semiconductor laser described above.

Note that the inclination of the plane orientation of the substrate surface from (ioo) is
Although it depends on the crystal growth conditions, the range of 2 to 5 [degrees] was the best from the viewpoint of steps, film thickness, etc., but the above slope was 0.
When the thickness was 5 [expansion] or more, sufficiently good results were obtained with respect to steps, film thickness, etc.

The present invention focuses on these points, and provides a compound semiconductor substrate having a zincblende crystal structure, a striped groove formed on this substrate, or a current confinement formed on the substrate in which the groove is formed. In the semiconductor laser device, the surface orientation of the surface of the substrate is set to the stripe of the groove. The plane is tilted at an angle of 70.5 degrees or more from the 100) plane with the direction as the axis.

Further, the present invention provides a semiconductor radar 1 having the above structure, which has a zinc blende crystal structure and whose main surface is (100) [1
Form a stripe-shaped groove in a direction perpendicular to the (100) direction of the substrate crystal on a compound semiconductor substrate tilted by 0.5 degrees or more from ii, or grow a current confinement layer on the substrate and then The constriction layer is selectively etched to a depth down to the substrate to form the grooves, and then all +? In this method, at least the first cladding layer, the active layer, and the second cladding layer and the second cladding layer are sequentially grown in step ii. It is also possible to easily fabricate a self-aligned semiconductor laser with excellent transverse mode control. It is extremely effective for this purpose. Also, striped grooves? : Since it is formed in the current confinement layer, the transverse mode control structure and the current confinement structure can be realized simultaneously in one process, which greatly simplifies the manufacturing process and improves productivity. From this point of view as well, it is effective for production and cost reduction. Furthermore, since various crystal growth layers can be formed using the MOCvD method, it is possible to grow homogeneous film crystals, thereby improving the reliability of semiconductor radars.

[Embodiments of the invention]

FIG. 1 is a perspective view showing a schematic structure of a semiconductor laser according to an embodiment of the present invention, and FIG. 2 is a perspective view showing a manufacturing process of the laser.

First, from the <(100) plane as shown in Figure 2 (-), (01
1) p-GaAs with a plane orientation tilted 2 degrees in the direction
'4@, 1, an n-GaAs layer (
(current confinement layer) is epitaxially grown to a thickness of about 2 ft, 1 (μm).This crystal growth does not necessarily require MO
Although it is not necessary to use the CVD method, the MOCVD method is advantageous because it can provide a thin film crystal with good uniformity in thickness over a large area. Next, photorenost (
The current confinement layer 2 is selectively etched using a mask (not shown) to form striped grooves 2at- reaching the substrate 1 in the <011> direction. This etching can be performed, for example, with CH3
0H1I (3PO4, H20□ (volume ratio 3:1:1)%
This can be done using an etching solution.

Next, p-"o,
55AtO, 45” layer (cladding layer) 3, undoped 0
110.135AZ, 15A11 layer (active layer) 4, n
-Ga. , □A to 45"1?1i (cladding layer) 5,
and n-GaAs layer (contact) M) 6't are sequentially epitaxially grown. In this case, the substrate in the state shown in FIG. 2(b) is thoroughly degreased and cleaned, the natural oxidation layer on the surface is removed by HCI, etc., and the substrate is immediately placed in a reactor. The raw material is trimethylgallium ((CH,)3GIL
), trimethylaluminum (' (CHρ3At)
, using arsine gas (AsH3), noethylzinc ((C2H5)2zn) as a p-type compound, and hydrogen selenide gas (H2Se) as an n-type compound.
f: Used. Growth temperature 750 [℃], Il in source gas
Group I elements (Ga.

ht ) and group V element is [:AI! ]/([G
Crystal growth was performed under the conditions of a ]+[:A/ri)=20 lλ
As a result, the width of the core provided on the board was 3 (tsn),
(@The thickness is 1 [μm'3. The thickness of the club layer 3 is 2 (t
an :], the active layer 4 has a step as shown in FIG.
On one surface of the substrate 1, an ohmic electrode of An-Zn is provided.
/ Au 8? ]l-, a semiconductor laser device having the structure shown in FIG. 1 can be obtained.

As can be seen from FIG. 1, the semiconductor laser thus manufactured has a step at the upper part of the groove 2a, and the film thickness thereof is significantly thicker than in other parts. For this reason, the light confinement effect becomes a dog, and stable transverse mode control is performed. I can do two things. In addition, each crystal layer 2. ~,7 is MO(:
Since it is formed by the VD method, the crystal layer 2. . Furthermore, the strizoidal groove 2a formed in the current confinement layer 2 has a narrow flow 4->X structure and Tsuge mode iii! I Onjuku-zukuri and Onjuku-zukuri can be realized simultaneously in one process. This method is extremely effective in increasing production and lowering costs of Shikka-c1 semiconductor lasers.

Note that the present invention is limited to the above-mentioned contract example.
do not have. For example, as another example of the double heterojunction structure described in 1iiJ, as shown in FIG. Good too. In this case, since the laser light is guided along the IL of the optical guide layer 1, the mode size that falls on the resonator end face becomes large. As a result, optical constancy and optical absorption at the resonator end faces are small, end-to-end destruction is less likely to occur, and a large optical output can be obtained. Moreover, since the beam radiation angle in the direction perpendicular to the active layer can be made small, there is an advantage that it is easy to obtain an isotropic beam.

In addition, in the actual example, we used the old rate of GaAlAs,
Instead, IHGaA*P, AZGAAJP, InA7GaP, or the like may be used, and the material is not particularly limited. Furthermore, the formation of each crystal layer is not necessarily MOCV
The method is not limited to the D method, and it is also possible to use the conventional i, Pg 4- method. Also: Tomoitaiwa! IIi (100
) is limited to 2 + Hh4 vc, and d,
It is sufficient that the temperature is not less than 0.5 degrees (preferably 2 to 5 degrees). It is also possible to completely form a Nutlig-like groove on the surface of the Nord plate without using one current confinement layer, and to provide a Pete D joint rtg structure on the glued plate. others,
Various modifications can be made without departing from the spirit of the invention.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a schematic structure of a semiconductor laser according to an embodiment of the present invention, FIG. 2 is a perspective view showing the JM manufacturing process of the above 1/-de, and FIG. 3 is a perspective view showing a modified example. , is. 1- p-GnAs substrate, 2- F city to n-G steam,
Narrow 2ν layer, J =・p −”0.55A40.45A
9 cladding layers, 4...Andoso Gao85Ato1
5A! +Active layer, 5”・n −Glin, L n to 5
4sAl'1 cladding layer, 6...n GaAs contact layer, 7...Au-Go/Au ohmic'a4IB-4u-Zn/Au ohmic tit pole, 1no...n-CJ &0. 65 AZo3s
A! ! light guide layer. Applicant's agent Patent attorney Takehiko Suzue 21", 1 Figure 3

Claims (8)

[Claims] (1) A compound semiconductor substrate having a zincblende crystal structure with striped Y14 formed on the surface and a heterojunction structure grown on the substrate with the active layer sandwiched between cladding layers. The plane orientation of the surface of the substrate is 90 degrees from the toe plane with the stripe direction of the groove as the axis.
．． A semiconductor laser device characterized in that it is tilted by 5 degrees or more. (2) A compound semiconductor substrate having a zincblende crystal structure, a low-flow constriction layer provided on the substrate and having striped grooves formed therein, and an active layer sandwiched between cladding and cladding layers. the substrate and a heterojunction structure grown on the current confinement layer; A semiconductor laser device characterized in that: (3) The current confinement layer is composed of a semiconductor layer having a conductivity type opposite to that of the substrate or a semiconductor layer having a high resistance.
The semiconductor laser device according to claim 2, characterized in that: t-characteristic. (4) It has a zincblende crystal structure and its main surface is (100
) Face! A process of forming stripe-shaped grooves in a direction perpendicular to the (100) direction of the substrate crystal on a compound semiconductor substrate tilted by 00.5 degrees or more, and then forming at least a first cladding layer, an active layer and a second cladding layer on the entire surface. 1. A method of manufacturing a semiconductor laser device, comprising a step of sequentially growing and forming layers. (5) The semiconductor according to claim 4, characterized in that a metal vapor phase epitaxy method is used as a method for growing the active layer, first and second cladding and cladding layers. A method for manufacturing a laser device. (6) It has a zincblende crystal structure and its main surface is (100
) Current confinement rfI on a compound semiconductor substrate tilted more than 0.5 degrees from the plane? : A step of growing and forming the current confinement layer, a step of selectively etching the current confinement layer to a depth reaching the substrate to form a stripe-shaped groove in a direction perpendicular to the (100) direction of the substrate crystal, and then etching at least a first cladding layer over the entire surface. 1. A method for manufacturing a semiconductor radar device, comprising a step of sequentially growing a layer, an active layer, and a second cladding layer. (7) The method for manufacturing a semiconductor laser device according to claim 6, wherein a semiconductor layer having a conductivity type opposite to that of the substrate or a high resistance semiconductor layer is used as the current confinement layer. (8) The semiconductor according to claim 6, characterized in that the current confinement layer, the active layer, and the first and second cladding layers are grown using metal organic vapor phase epitaxy. A method for manufacturing a laser device.