JP2641540B2 - Method for forming epitaxial crystal layer and method for manufacturing stripe type semiconductor laser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to an epitaxial crystal layer forming method for simultaneously growing epitaxial crystal layers having different properties on a crystal substrate, and more particularly to a method of forming a stripe type semiconductor laser in which light is confined in a stripe-shaped active region. Regarding a manufacturing method, an object of the present invention is to provide an epitaxial crystal layer forming method capable of simultaneously growing epitaxial crystal layers of different properties, wherein different crystal plane orientations are exposed in a first region and a second region. The above-described first method is performed by growing an epitaxial crystal layer on a crystal substrate by an epitaxial crystal growth method in which a decomposition reaction of organometallic molecules including atoms constituting the epitaxial crystal layer to be formed governs the growth on the substrate surface. The epitaxial crystal layers having different properties are simultaneously formed on the region and the second region. It is configured to grow.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epitaxial crystal layer forming method for simultaneously growing epitaxial crystal layers having different properties on a crystal substrate, and more particularly to a method of forming a stripe type semiconductor laser in which light is confined in a stripe-shaped active region. It relates to a manufacturing method.

[Related Art] In recent years, semiconductor lasers have been regarded as important as a light source for high-speed optical communication and as a light source for recording / reproducing of compact disks and laser disks, and the demand has been increasing. Currently used semiconductor lasers are mainly of a stripe type in which light is confined in a stripe-shaped active region.

In a striped semiconductor laser, a light confinement layer with different properties must be formed around the active layer. However, conventionally, crystal layers with different properties cannot be grown simultaneously. Was. That is, after a semiconductor laser structure is formed on a substrate, it is taken out of a crystal growth apparatus, mesa processing is performed to deposit an insulating film, and then ion implantation, impurity diffusion,
A stripe type semiconductor laser has been manufactured by performing processes such as crystal regrowth. In particular, taking out the semiconductor laser from the crystal growth apparatus during the manufacturing process has caused a decrease in yield.

[Problems to be Solved by the Invention] As described above, conventionally, it is impossible to simultaneously grow crystal layers having different properties, so that an extremely complicated process is required to manufacture a stripe type semiconductor laser, and the yield is improved. Not only is it difficult but also an obstacle to cost reduction.

An object of the present invention is to provide an epitaxial crystal layer forming method capable of simultaneously growing epitaxial crystal layers having different properties.

Another object of the present invention is to provide a method of manufacturing a stripe-type semiconductor laser that can be manufactured consistently in a crystal growth apparatus without taking out the semiconductor laser during manufacturing.

[Means for Solving the Problems] The object described above includes atoms constituting an epitaxial crystal layer to be formed on a crystal substrate in which different crystal plane orientations are exposed in a first region and a second region. By growing the epitaxial crystal layer by an epitaxial crystal growth method in which the decomposition reaction of the organometallic molecules on the substrate surface governs the growth, an epitaxial crystal layer having different properties is formed on the first region and the second region. This is achieved by a method of forming an epitaxial crystal layer, characterized in that they are grown simultaneously.

Another object of the present invention is to expose a stripe region where an active layer is to be formed on the (311) A surface or the (311) B surface (10
By depositing Al _x Ga _{1 -x} As at a first predetermined temperature on a GaAs substrate of the 0) plane by a gas source molecular beam epitaxy method that supplies at least Al and Ga in the form of organometallic molecules, Forming a first clad layer having an Al composition ratio of x1, and depositing Al _x Ga _1-x As on the first clad layer at a second predetermined temperature by the gas source epitaxy method. The first composition ratio on the stripe region
An active layer having a second Al composition ratio x2 lower than x1 is formed, and a light confinement layer having a third Al composition ratio x3 higher than the second Al composition ratio x2 is formed on a region around the stripe region. And depositing Al _x Ga _{1 -x} As at the first predetermined temperature on the active layer and the light confinement layer by the gas source molecular beam epitaxy method. Forming a second cladding layer having a ratio x1.

[Operation] According to the present invention, epitaxial crystal layers having different crystal plane orientations are exposed on a crystal substrate and epitaxial crystal layers having different properties can be simultaneously grown. For this reason, it is possible to manufacture a stripe-type semiconductor laser in which light confinement layers having different properties are formed around the active layer without taking out the crystal growth apparatus during the manufacturing.

Embodiment A method for forming an epitaxial crystal layer according to an embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows a gas source molecular beam epitaxy apparatus used in the present invention. Chamber where crystal growth takes place
An exhaust pipe 12 is provided in the exhaust pipe 12, and the chamber 10 is evacuated from the exhaust pipe 12 to a high vacuum by a diffusion pump (not shown). A holder 14 made of molybdenum is provided in the chamber 10, and a GaAs substrate 16 for growing a crystal is held in the holder 14. The holder 18 has a heater 18 embedded therein.
By controlling the current flowing through 18, the temperature of the GaAs substrate 16 can be controlled. In addition, RH
An RHEED screen 22 is provided below the EED gun 20.

In order to supply each material as a source for crystal growth, in this embodiment, four cells 24, 25, 26,
27 are provided. The top cell 24 contains solid Be as a p-type dopant. Second cell 25
Is a source of Al, TEA (triethylaluminium)
And gas introduction pipes 25a and 25b for supplying TEG (triethyl gallium) which is a source of Ga and Ga. TEA
And the amount of TEG introduced can be adjusted by valves 25c and 25d provided in gas introduction pipes 25a and 25b. The third cell 26 stores solid As. The fourth cell contains solid Si as an n-type dopant. Cells 24, 2
The shutters 28, 29, 30, and 31 are provided at 5, 26, and 27, respectively, so that the supply of each material can be controlled.

The exhaust pipe 12, the RHEED gun 20, and the RHEED
Portions other than the screen 22 and the cells 24, 25, 26, 27 are covered with a liquid nitrogen shroud 32.

The inventor of the present application performed an experiment of epitaxially growing Al _x Ga _{1 -x} As on a GaAs substrate using the gas source molecular beam epitaxy apparatus shown in FIG. 1, and obtained an interesting experimental result as shown in FIG. Obtained. The results of this experiment will be described.

First, a GaAs substrate with a (100) face exposed and a (311) A
A GaAs substrate having a surface exposed and a GaAs substrate having a (311) B surface exposed are prepared. These (100) GaAs substrates,
An Al _x Ga _{1 -x} As layer is grown on the (311) A-plane GaAs substrate and the (311) B-plane GaAs substrate by the gas source molecular beam epitaxy apparatus shown in FIG.

A GaAs substrate 16 for growing a crystal is held in a holder 14 of the gas source molecular beam epitaxy apparatus shown in FIG. While heating the holder 14 by the heater 18 to adjust the temperature, the shutters 29 and 30 are opened and the valves 25a and 25b are opened to open the cell 26.
Heat. As a result, the Al _x G
a _1-x As crystal grows. FIG. 2 is a graph showing the relationship between the Al composition ratio x of the crystal grown Al _x Ga _{1 -x} As and the temperature of the GaAs substrate 16 during the crystal growth. The As pressure at this time is
1.7 × 10 ^-5 Torr.

As can be seen from FIG. 2, in the case of the (100) plane, although the Al composition ratio x of the crystal grown Al _x Ga _{1 -x} As does not change much with the GaAs substrate temperature, the (311) A plane and the (311) In the case of plane B, it was found that there was a strong correlation between the Al composition ratio x of Al _x Ga _{1 -x} As and the temperature of the GaAs substrate. That is, (31
1) In the case of plane A, when the temperature of the GaAs substrate increases, the Al composition ratio x increases.
l The composition ratio x decreases conversely.

This embodiment is based on the above experimental results, and the (100) plane GaAs substrate is etched to partially (31).
1) A surface or (311) B surface is exposed, and Al _x Ga _1-x As is placed on a (100) surface and a (311) A surface or a (311) B surface GaAs substrate.
Al _x Ga with different Al composition ratios
_1-x As is formed at the same time.

The surface processing of the GaAs substrate will be described with reference to FIG.

First, a mask layer 42 of silicon oxide, nitrogen silicon, or the like is formed on the entire surface of a GaAs substrate 40 (FIG. 3A). Next, the mask layer 42 in the area to be exposed is removed by photolithography (FIG. 3B). Then (31
1) A GaAs substrate exposed with a surface-etching etchant (50: 1: 50 mixture of phosphoric acid (H ₃ PO ₄ ), hydrogen peroxide solution (H ₂ O ₂ ) and water (H ₂ O)) Etch 40 surfaces. Then, as shown in FIG. 3 (c), the central portion of the etched region becomes the (100) plane and the periphery becomes the (311) A plane or the (311) B plane. After that, the mask layer 42 is removed and the surfacing process is completed (FIG. 3D).

Thus, (100) plane and (311) A plane or (311) plane
An Al _x Ga _{1 -x} As layer is deposited on the GaAs substrate 40 having the exposed B surface by a gas source molecular beam epitaxy method. At this time, when the temperature of the GaAs substrate is controlled, Al _x Ga _{1 -x} As layers having different Al composition ratios x are simultaneously formed on the GaAs substrate.

That is, Ga having the (100) plane and the (311) A plane
In the case of an As substrate, if the GaAs substrate temperature is set to, for example, 520 ° C., an Al _0.25 Ga having an Al composition ratio x of about 0.25 is formed on the (100) plane.
_{A 0.75} As layer is formed, and an Al _0.1 Ga _0.9 As layer having an Al composition ratio x of about 0.1 is formed on the (311) A plane. In the case of a GaAs substrate having the (100) plane and the (311) B plane exposed, GaAs
s If the substrate temperature is 630 ° C, for example,
An Al _0.32 Ga _0.68 As layer having a composition ratio x of about 0.32 is formed.
1) An Al _0.05 Ga _0.95 As layer having an Al composition ratio x of about 0.05 is formed on the B surface.

Next, a method of manufacturing a stripe-type semiconductor laser according to another embodiment of the present invention will be described with reference to FIGS.

FIG. 4 shows a cross section of a stripe-type semiconductor laser manufactured according to this embodiment.

First, the (100) GaAs substrate 40 is formed by the method shown in FIG.
Next, the (311) A surface or the (311) B surface is subjected to surface finishing. Then, as shown in FIG.
A GaAs substrate for manufacturing a stripe-type semiconductor laser having a stripe-shaped (311) A surface or (311) B surface exposed at the center of the 0) surface is manufactured.

A case in which a stripe-type semiconductor laser is formed on a GaAs substrate having the (100) plane and the (311) B plane exposed will be described.

The GaAs substrate 50 is housed in the gas source molecular beam epitaxy apparatus shown in FIG. Heater 18
Temperature of the GaAs substrate 50 to about 520 ° C.
Opening 9, 30, and 31 and opening only the valve 25d allow crystal growth. Then, an n ⁺ -type GaAs layer having a thickness of about 2 μm and an impurity concentration of about 2 × 10 ¹⁸ cm ^-3 is formed on the GaAs substrate 50 as a buffer layer.
52 are formed.

Subsequently, the GaAs substrate temperature was kept at 520 ° C and the valve 25c
Is further opened to form an n-type Al _x Ga _{1 -x} As layer 54. Since the temperature of the GaAs substrate is 520 ° C., the (100) plane also shows (31
1) n-type Al _0.25 Ga _0.75 As with Al composition ratio x of about 0.25 on B side
Layer 54 is formed. The thickness of the n-type Al _0.25 Ga _0.75 As layer 54 is about 1.5 μm and the impurity concentration is about 3 × 10 ¹⁷ cm ⁻³ .

Next, the GaAs substrate 50 is heated by the heater 18 to bring the substrate temperature to about 630 ° C. Then, the shutter 31 is closed to perform crystal growth, and a p-type A of about 0.1 μm is formed on the n-type Al _0.25 Ga _0.75 As layer 54.
An l _x Ga _1-x As layer 56 is formed. Then, the p-type Al _x Ga _1-x As layer 5
6 is whether the surface of the underlying GaAs substrate 50 is the (100) surface (311)
The Al composition ratio x differs depending on whether the surface is the B surface. That is,
On the (100) plane, a p-type Al _0.32 Ga having an Al composition ratio x of about 0.32
_0.68 As layer 56a has an Al composition ratio x of about 0.05 on the (311) B surface.
The p-type Al _0.05 Ga _0.95 As layer 56b is formed at the same time. Therefore, the stripe-shaped p, which is an active layer having a high refractive index, is formed.
A stripe structure in which the p-type Al _0.32 Ga _0.68 As layer 56a, which is a light confinement layer having a low refractive index, in which the p-type Al _0.05 Ga _0.95 As layer 56b is completed at a time, is completed.

Next, the substrate temperature of the GaAs substrate 50 was returned to about 520 ° C.
A p-type Al _x Ga _1-x As layer 58 is formed on the type Al _0.32 Ga _0.68 As layer 56a and the p-type Al _0.05 Ga _0.95 As layer 56b. Since the substrate temperature is 520 ° C., a p-type Al _0.25 Ga _0.75 As layer 58 having an Al composition ratio x of about 0.25 is formed on both the (100) plane and the (311) B plane from FIG. The thickness of the p-type Al _0.25 Ga _0.75 As layer 58 is about 1.5 μm.
m and the impurity concentration is about 5 × 10 ¹⁷ cm ⁻³ .

Subsequently, the GaAs substrate temperature was kept at 520 ° C and the valve 25c
Is closed, and ap ⁺ -type GaAs layer 60 is formed on the p-type Al _0.25 Ga _0.75 As layer 58. This p ⁺ -type GaAs layer 60 has a thickness of about 0.5 μm and an impurity concentration of about 1 × 10 ¹⁹ cm ⁻³ . Thus, the structure of the main part of the stripe type semiconductor laser is completed.

The case of the GaAs substrate 50 with the (100) plane and the (311) A plane exposed is basically the same as the above-mentioned manufacturing method, but the GaAs substrate temperature during the manufacturing is different. That is, the n ⁺ type GaAs layer 52,
n-type Al _x Ga _1-x As layer 54, p-type Al _x Ga _1-x As layer 58, p ⁺ type GaAs layer
During the production of 60, the temperature of the GaAs substrate was 630 ° C and the p-type Al _x Ga _1-x A
At the time of manufacturing the s layer 56, the GaAs substrate temperature is set to 520 ° C. Then
From the graph of FIG. 2, the n-type Al _x Ga _1-x As layer 54 and the p-type Al _x Ga
The Al composition ratio x of the _1-x As layer 58 is about 0.3. p-type Al _x Ga _1-x As
The layer 56 is made of p-type Al having an Al composition ratio x of about 0.25 on the (100) plane.
_{A 0.25} Ga _0.75 As layer 56a is formed, and a p-type Al _0.1 Ga _0.9 As layer 56b having an Al composition ratio x of about 0.1 is formed on the (311) A plane.

As described above, according to this embodiment, the active layer and the optical confinement layer can be manufactured at the same time, so that the stripe structure can be manufactured without taking out the stripe structure from the gas source molecular beam epitaxy apparatus at all, and the yield rate is improved. And cost reduction is possible.

The present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, solid As was used as the source, but As may be introduced in the form of organometallic molecules.

In the above embodiment, the present invention is applied to the manufacture of a stripe type semiconductor laser. However, the present invention is also applied to the manufacture of other semiconductor devices which simultaneously form Al _x Ga _1-x As layers having different Al composition ratios x. Can be applied.

Furthermore, the present invention is not limited to the above-described embodiment, and when an epitaxial crystal layer is grown by an epitaxial crystal growth method in which a decomposition reaction of organometallic molecules on the substrate surface governs the growth on a crystal substrate having different crystal plane orientations. May be.

[Effects of the Invention] As described above, according to the present invention, it is possible to simultaneously grow epitaxial crystal layers having mutually different properties only by exposing different crystal plane orientations to the crystal substrate and performing epitaxial crystal growth. . Therefore, it is possible to manufacture a stripe-type semiconductor laser in which light confinement layers having different properties are formed around the active layer without removing the semiconductor laser from the inside of the crystal growth apparatus during the manufacturing process, thereby improving the yield and reducing the cost. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a gas source molecular beam epitaxy apparatus used in the present invention, FIG. 2 is a graph showing a relationship between a GaAs substrate temperature and an Al composition ratio by a manufacturing method of the present invention, and FIG. FIG. 4 is a sectional view of a stripe type semiconductor laser manufactured by the manufacturing method of the present invention. In the figure, 10 ... chamber, 12 ... exhaust pipe, 14 ... holder, 16 ... GaAs substrate, 18 ... heater, 20 ... RHEED gun, 22 ... RHEED screen, 24, 25, 26, 27 ... ... cells, 25a, 25b ... gas introduction tubes, 25c, 25d ... valves, 28, 29, 30, 31 ... shutters, 32 ... liquid nitrogen shrouds, 40 ... GaAs substrates, 42 ... mask layers, 50 ... n ⁺ type GaAs substrate, 52 ... n ⁺ type GaAs layer, 54 ... n type Al _0.25 Ga _0.75 As layer (or n type Al _0.3 Ga _0.7 As
56) p-type Al _x Ga _1-x As layer, 56a p-type Al _0.32 Ga _0.68 As layer (or p-type Al _0.25 Ga _0.75 A)
s layer), 56b ... p-type Al _0.05 Ga _0.95 As layer (or p-type Al _0.11 Ga _0.9 As)
58) p-type Al _0.25 Ga _0.75 As layer (or p-type Al _0.3 Ga _0.7 As
Layer), 60 ... p ⁺ type GaAs layer.

Claims (3)

(57) [Claims] An organic metal molecule containing atoms constituting an epitaxial crystal layer to be formed is formed on a crystal substrate having different crystal plane orientations in a first region and a second region. An epitaxial crystal layer having different properties is simultaneously grown on the first region and the second region by growing the epitaxial crystal layer by an epitaxial crystal growth method in which a decomposition reaction governs the growth. An epitaxial crystal layer forming method. 2. The (100) plane in the first area is (3) in the second area.
11) An Al _x Ga _1-x As layer is formed on a GaAs substrate having a surface A or a surface (311) B by a gas source molecular beam epitaxy method in which at least Al and Ga are supplied in the form of organometallic molecules. By depositing at a temperature, Al having an Al composition ratio x different from each other is formed on the first region and the second region.
_A method for forming an epitaxial crystal layer, comprising forming an _x Ga _1-x As layer. 3. A (100) plane GaAs substrate having a stripe region on which an active layer is to be formed on a (311) A plane or a (311) B plane. By gas source molecular beam epitaxy
_x Ga _1-x As is deposited at a first predetermined temperature,
Forming a first cladding layer having an Al composition ratio of x1, and depositing Al _x Ga _{1 -x} As on the first cladding layer at a second predetermined temperature by the gas source epitaxy method. An active layer having a second Al composition ratio x2 lower than the first composition ratio x1 on the stripe region is formed, and a third Al region higher than the second Al composition ratio x2 is formed on a region around the stripe region. Forming a light confinement layer having an Al composition ratio x3, and forming Al _x Ga _1-x As at the first predetermined temperature on the active layer and the light confinement layer by the gas source molecular beam epitaxy method. Forming a second cladding layer having the first Al composition ratio x1 by depositing. 2. A method for manufacturing a stripe-type semiconductor laser, comprising: