JPH04192515A - Manufacture of semiconductor quantum well box - Google Patents

Abstract

PURPOSE:To enable manufacture of a variety of optical devices utilizing characteristics of a quantum well box by realizing growth of fine crystal to form a semiconductor quantum well box on a surface of a compound semiconductor. CONSTITUTION:An AlGaAs layer 2, which is a crystal layer of a second compound semiconductor is grown on the face (100) of GaAs substrate 1 consisting of a first compound semiconductor. A part of this surface is covered with a photoresist and the etching is then carried out with the photoresist used as a mask. Thereby, the face (111) is exposed to the side surface to form the stepped portion 3 on the substrate surface. After the photoresist is removed, a AlGaAs layer 4, which is a crystal layer of the same composition as the second compound semiconductor is grown. Next, a GaAs fine crystal 5 of the regular tetrahedron, which is a fine crystal of a third compound semiconductor, is grown on the side surface of the stepped part. Thereafter, an AlGaAs layer 6 which is a crystal of a fourth compound semiconductor is grown. Accordingly, a quantum well box structure is formed and it can be used directly as a waveguide and a semiconductor laser and an optical switch can be manufactured by forming electrodes thereto.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method of manufacturing a semiconductor quantum well box, and is particularly concerned with a method for manufacturing a semiconductor quantum well box, and is particularly applicable to nonlinear materials such as high-performance semiconductor laser materials or ultra-high-speed optical switches and optical logic devices. This invention relates to materials with large nonlinear optical constants, which are necessary for realizing light control elements with optical effects.

<Prior art> As a method for manufacturing a semiconductor quantum well box, GaAs (111
) It is known that triangular bell-shaped GaAs microcrystals can be formed on a substrate by organometallic vapor phase epitaxy (37th Japan Society of Applied Physics Related Conference 31a-D-6). This is Ga
As (111) B surface (As surface) or A surface (Ga surface)
An A I GaAs layer is grown on the (111) A-plane (or B-plane), and then a tetrahedral GaAs microcrystal with a side of several tens of nanometers surrounded by the (111) A-plane (or B-plane) is grown.
Further, an Aj2-GaAs layer is grown thereon to cover the microcrystals.

<Problem to be solved by the invention> However, in the conventional method for manufacturing semiconductor quantum well boxes, a GaAs (111) substrate is used, but in this case, the range of conditions for crystal growth while maintaining a mirror state is narrow. , and it is difficult to determine a specific crystal axis direction on the substrate surface. This is a serious drawback especially when a plurality of different elements are integrated on the same substrate.

Means for Solving the Problems> In order to solve the above-mentioned drawbacks, the present invention provides a wide range of growth conditions for obtaining a mirror-like surface state when layered crystal growth of a compound semiconductor is performed, and also provides a method for forming a waveguide. When forming a compound semiconductor, the (100) plane of the compound semiconductor, which can easily match the direction of light propagation and the direction of the crystal axis, is used, and the sides are (111) planes along the <110> direction. The sides of a certain step or groove are formed and microcrystals are grown on these sides to form a semiconductor quantum well box. That is, the present invention provides a semiconductor substrate (100
) a step of growing a crystal layer of a second compound semiconductor having a zincblende crystal structure on a surface, and a step of growing a crystal layer of a second compound semiconductor having a zincblende crystal structure on a surface thereof, and growing the crystal layer of the second compound semiconductor along the direction
111) A step of forming a step or groove-like side portion that is a plane, and growing microcrystals of a third compound semiconductor having a smaller band gap than the second compound semiconductor directly at the position of the step or groove-like side portion. or a step of forming the same crystal layer as the second compound semiconductor having the zinc blende crystal structure on the surface of the crystal layer on which the step or groove-like side portion is formed;
After growing the layer so that the layer thickness is smaller than the depth of the side portion of the step or groove, the second compound semiconductor is placed on the same layer as the second compound semiconductor at the position corresponding to the side of the step or groove. A step of growing a third compound semiconductor microcrystal having a smaller band gap than the second compound semiconductor, and a step of growing a third compound semiconductor microcrystal having a larger hand gear than the third compound semiconductor so as to cover the third compound semiconductor microcrystal. This is a method for manufacturing a semiconductor quantum well box, which comprises the step of growing a crystal layer of a compound semiconductor in step 4.

Effect> The present invention facilitates the formation of a plurality of different semiconductor elements by using the (100) plane of a compound semiconductor substrate, and also uses microcrystals to form a semiconductor quantum well box on the (111) plane of the compound semiconductor. growth can take place.

<Example> Examples of the present invention will be described below.

(Example 1) First, a GaAs substrate 1 (10
A second compound semiconductor crystal layer is formed using trimethylgallium (T?IG) and trimethylaluminum as raw materials by organometallic vapor phase epitaxy on the 0) plane (off-plane of about 0.5 degrees is also acceptable).
A GaAs layer (2) is grown to a thickness of about 2 μm. Furthermore, A
The J composition is set to 0.3. At this time, the growth temperature is 750-8
The temperature is set in the range of 00°C, and the molar ratio of As to Ga and A1 (V-III ratio) is 20 to 50. A portion of this surface is then covered with photoresist so that its edges are along the <011> direction. Using this as a mask, HgS with a composition ratio of 5:l:1
When etching is performed using an O4:HzO□, H20-based etching solution, a step with the (111) plane exposed on the side surface as shown in FIG. 2 is formed on the substrate surface. Here, the height difference 3 was controlled to 1 μm. After removing the photoresist, this substrate was reintroduced into the furnace of the organometallic vapor phase epitaxy apparatus, and a crystal layer having the same composition as the second compound semiconductor was grown under the same conditions as above.
I GaAs layer 4 is 0. Grow to 1 μm (Figure 1). This is to obtain a clean surface 4 of the second compound semiconductor crystal layer since the second compound semiconductor crystal layer 2 comes into contact with the etching solution or air and becomes a dirty surface due to the etching process. Therefore, the crystal layer 4 can also be omitted. Next, after the growth of the crystal layer 4, the supply of TMG and TMA was stopped, and the substrate temperature was raised to 7°C while only arsine was flowing.
The temperature drops to 20°C. By supplying TMG again for 10 seconds in this state, a tetrahedral GaAs microcrystal 5, which is a third compound semiconductor microcrystal, grows on the side surface of the stepped portion. After this, the temperature was raised again and the fourth temperature was raised under the same conditions as above.
An A I GaAs layer 6, which is a compound semiconductor crystal, is grown.

Through the above steps, a quantum well box structure having a cross section as shown in FIG. 1 was formed. This structure can be used as a waveguide as it is, and by forming electrodes on it, semiconductor lasers, optical switches, etc. can be manufactured. Further, this waveguide is easy to form into an array, and is also suitable for forming other elements on the (100) plane other than the step portion and integrating this and the above elements.

The above steps are just examples, and can be modified in various ways as necessary. For example, the etching solution is not limited to those mentioned above, as long as it is selected to have a composition that etches the (111) plane at a slower rate than other planes. Other crystal growth methods such as molecular beam epitaxy can also be used if conditions are set appropriately. In addition, although the GaAs/A I GaAs system has been described here, the A I GaAs/A I GaAs system with a different composition
A similar quantum well box can be manufactured by selecting an appropriate etching solution and setting crystal growth conditions for the S or InP/InGaAsP system.

(Example 2) A second example will be described. As shown in Figure 4, first GaA
s (100) The same conditions as in Example 1 were applied on the substrate 7.
'jl (yaAsJLf 8) is grown. A resist is applied to this surface, and a striped pattern with a period of about 0.25 μm is formed using a method such as three-beam interference exposure method.
＞・Expose and pattern along the direction. Next, using this as a mask, A I was applied using the same etching solution as in Example 1.
When the surface of the GaAs layer is etched, a groove-like structure 9 having a triangular cross section as shown in FIG. 4 can be formed. At this time, the (111) plane and the (111) plane are exposed on the surface.

On this surface, as shown in FIG. 3, A I! GaAs layer 1
0 to a thickness of 50 nm (this layer can be omitted as in Example 1). Thereafter, as in Example 1, Ga
As microcrystals 11 are formed on the side surfaces of the groove, and A I Ga
The As layer 12 is grown. A I GaAs layer 12 3
When grown to a thickness of about μm, the surface can be made almost flat. A cross-sectional view of the finally formed quantum well box structure is shown in FIG. Forming electrodes on this flat surface,
It is also possible to stack other elements. Similar to the first embodiment, the above steps can be modified in various ways.

<Effects of the Invention> According to the present invention, using a GaAs (100) substrate,
Waveguide structures including quantum well boxes can be easily fabricated.

This makes it possible to manufacture various optical devices using the characteristics of quantum well boxes.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention, in which FIG. 1 is a sectional view of a semiconductor quantum well box, FIG. 2 is a perspective view of a substrate after etching in embodiment 1, and FIG. 3 is a cross-sectional view of a semiconductor quantum well box. FIG. 4, a sectional view of a semiconductor quantum well box showing an embodiment, is a perspective view of a substrate after etching in Example 2. 1.7: GaAs substrate, 2.8rAIGaAs layer, 4,
10: A I GaAs layer, 5. 11: GaA
s1i crystal, 6.12: A j! GaAs layer (0'lT) surface Figure 1 Figure 2

Claims (1)

[Claims] (1) A semiconductor substrate made of a first compound semiconductor (100
) a step of growing a crystal layer of a second compound semiconductor having a zincblende crystal structure on a surface, and a step of growing a crystal layer of a second compound semiconductor having a zinc blende crystal structure on a surface thereof, and a side surface of the crystal layer of the second compound semiconductor along the <110> direction.
111) A step of forming a step or groove-like side portion that is a plane, and growing microcrystals of a third compound semiconductor having a smaller band gap than the second compound semiconductor directly at the position of the step or groove-like side portion. or a step of forming the same crystal layer as the second compound semiconductor having the zinc blende crystal structure on the surface of the crystal layer on which the step or groove-like side portion is formed;
After growing the layer so that the layer thickness is smaller than the depth of the side portion of the step or groove, the layer is grown on the same crystal layer as the second compound semiconductor at the position corresponding to the side of the step or groove. A step of growing a third compound semiconductor microcrystal having a smaller band gap than the second compound semiconductor, and a step of growing a third compound semiconductor microcrystal so as to cover the third compound semiconductor microcrystal.
A method for manufacturing a semiconductor quantum well box comprising the step of growing a crystal layer of a fourth compound semiconductor having a larger bandgap than that of the compound semiconductor.