JPH0141261B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a semiconductor device.

Traditionally, a crystal layer is grown on a grooved substrate,
Methods for manufacturing semiconductor devices are widely used. As an example, a semiconductor laser is shown in FIG. N-type GaAs substrate 1 with a groove 1' of a constant width
On top is a first n-type Ga _1-x Al _x As cladding layer 2, a second
Layer non-doped Ga _1-y Al _y As active layer 3, third layer p-type
A Ga _1-x Al _x As cladding layer 4 and a fourth n-type GaAs current limiting layer 5 are successively grown, zinc diffusion is formed 6 directly above the groove in a stripe form from the crystal surface, and a p-side ohmic electrode 7 is provided. Further, an n-side ohmic electrode 8 is formed on the substrate side to complete the process. By adopting this structure, it is possible to oscillate in the active layer 3 above the groove, create an effective refractive index difference in the active layer 3 between the groove and the flat part, and provide a waveguide mechanism, so that the oscillated light can be transmitted above the groove. This stabilizes the transverse mode of oscillation.

Incidentally, the groove has a constant width, and the current situation is that there are almost no semiconductor devices constructed on a substrate with a varying groove width.

The present invention provides a semiconductor element that utilizes a crystal layer with a new shape obtained by growing crystals on a substrate with grooves having different groove widths within the same groove.

A groove 9' having a tapered width varying in width is provided on a single crystal semiconductor substrate 9, for example as shown in FIG. 2a.
Crystal growth is performed on the surface of the substrate by a liquid phase epitaxial method. In addition, Fig. 2 b, c, shown below
In d, A and B show views seen from directions A and B, respectively. By the way, when crystal growth is performed on a substrate having grooves in this way, generally speaking, if the degree of supersaturation of the solution at the start of growth is made small, the growth rate at the corners of the grooves 9' will be faster than that at the flat areas of the substrate 9. becomes larger, and the groove 9' becomes the grown crystal layer 10.
indicates a tendency to be filled with (Fig. 2b), that is, even if the groove 9' has a changed width as shown in the figure,
A growth layer 10 that is flat as a whole can be formed. On the other hand, if the degree of supersaturation is increased, the growth rate of the flat part of the substrate increases, and in order to fill the groove part, the growth layer 10' in the flat part must be made thicker, as shown in FIG. 2c. In other words, this means that by making the growth layer thinner, the thickness of the corner portion of the groove and the other flat portions (the flat portion inside the groove and the flat portion outside the groove) can be changed.

Furthermore, the thickness of the grown layer on the flat portion and the corner portions of the groove 9' can be changed by changing the depth, width, etc. of the groove 9'.

By utilizing such characteristics, it is possible to obtain a crystal layer 10'' having a shape as shown in FIG. 2d. That is, the structure shown in FIG. The growth layer 10'' was flat, thick at the corners of the groove 9' on the wide X'Y' side, and thin at the flat parts inside the groove 9' and the flat parts outside the groove 9'. It is something.

The crystal growth on the substrate having this new formation and the semiconductor element of the embodiment of the present invention that can be manufactured using the crystal growth will be specifically described below. less than
A simple optical waveguide is shown here as a semiconductor device by growing crystals of GaAs and Ga _1-x Al _x As using GaAs as a substrate.

Figure 2a is placed on the n-type GaAs crystal substrate 9 (100) plane.
A groove 9' having a varying width is formed as shown in FIG.
One of the edges of the groove 9' is oriented in the <011> direction, and the other is oriented at 30° with respect to it. The depth of groove 9' is
It is 1.5 μm. For example, n-type Ca _0.65 Al _0.35 As ₁₁ and non-doped GaAs ₁₂ are successively grown on this substrate 9 by a liquid phase epitaxial method.

When the degree of supersaturation at the start of growth is increased to 6°C, the growth starting temperature is 750°C, and the cooling rate is 0.5°C/min, the growth rate in the flat part becomes faster and the groove 9' is formed as shown in Figure 3. The first layer is n-type.
The surface of 21 made of GaAlAs is not flat.
Therefore, the second layer 22 made of GaAs has a flat shape on the narrow side of the groove and a slanted shape on the wide side of the groove. The film thickness of the first layer 21 at the flat part 21' is 0.5 μm, about 1 μm at the stepped portion 21'' of the wide groove corner, and the thickness of the second layer 22 is 0.5 μm at the flat part 22'. , at the sloped part 22'' of the step.
It can grow thicker than the flat part 22'' at 0.6 μm.

Therefore, since the inclined portion 22'' of the second layer GaAs 22 is thicker than both sides thereof, light can be confined in that portion and an optical waveguide can be formed.

In the structure shown in FIG. 3, the layer 22 has a refractive index distribution in the lateral direction on the narrow XY side.
Light propagates to the dotted area. On the wide X'Y' side, the 21" part is thick and the 21' part is thin, so the effective refractive index of 21" is high, and the light is
In other words, as shown in FIG. 3, as the incident light l ₄ travels through the layer 22, it does not spread laterally and is confined in the slanted portion. 22″ and is released from there. By using the waveguide structure shown in Figure 3, it is possible to change the plane of polarization of the incident light and the output light, which allows for diversification of usage conditions and is convenient for integration with laser elements, integration of optical ICs, etc. It is.

In this way, the optical waveguide shown in FIG.
Because it is twisted in the narrow and wide areas, it has the characteristic that when parallel polarized light is incident on the growth layer, light with a different polarization direction compared to the original incident light is obtained. There is.

The above examples show specific examples of GaAs and Ga _1-x Al _x As based semiconductor substrates in which the groove width changes in a tapered manner; however, the present invention is not limited to this. Alternatively, even if other materials are used, an optical waveguide with a varying groove width can be formed by growing a crystal with a higher refractive index than the substrate so that the surface is flat. Further, although the above description has been made regarding optical devices, it can be widely used in manufacturing other devices as well.

As described above, the present invention greatly contributes to the realization of semiconductor devices with excellent characteristics.
This brings about excellent effects in the use of optical devices and the like.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a conventional semiconductor laser constructed on a substrate with grooves, FIG. 2a is a perspective view of an example of a substrate used in the present invention having grooves with varying groove widths, and FIG. 2b -d are cross-sectional views of the crystals grown on the above substrate, A and B are cross-sectional views taken from directions A and B of Fig. 2a, and Fig. 3 is a cross-sectional view of two crystal layers grown on the substrate. A and B are cross-sectional views in the same A and B directions. 9...n-type GaAs substrate, 10, 10', 10''...
...Non-doped GaAs layer, 21...n-type Ga _1-x Al _x As
Layer 22...non-doped GaAs layer.

Claims (1)

[Claims] 1. A groove whose groove width is asymmetrical with respect to the groove direction and tapered is formed on the surface of a semiconductor substrate, a crystal layer is formed as an optical waveguide layer on the semiconductor substrate, and the crystal layer is A semiconductor device characterized in that a wide side of the groove is curved toward the substrate at a corner portion of the groove.