JP2000277435A - Growth method for garium nitride group compound semiconductor crystal and semiconductor crystal base material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a growth method for obtaining a high-quality epitaxial film by reducing the dislocation density without using a mask material, related to an epitaxial growth of a GaN group compound semiconductor crystal. SOLUTION: After a GaN group compound semiconductor film 2 is formed on the surface of a substrate 1, an SiO2 pattern 3 is formed over it, then the pattern 3 is evaporated in an atmosphere containing hydrogen so that an anti- surfactant region (Si residue part 4) is selectively formed. While a void 5 is formed on the anti-surfactant region, a GaN group compound semiconductor crystal 20 is epitaxial-grown. Since a dislocation line 6 is shielded with the void 5, the GaN group compound semiconductor crystal 20 of high quality is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a GaN compound semiconductor crystal and a semiconductor crystal substrate.

[0002]

2. Description of the Related Art Epitaxial growth of GaN-based compound semiconductor crystals is generally performed on a sapphire substrate or the like via a buffer layer because it is difficult to obtain a lattice-matched substrate. In this case, defects are introduced from the growth interface due to lattice mismatch between the epitaxial film and the substrate, and dislocations on the order of about 10 ¹⁰ cm ⁻¹ exist on the surface of the epitaxial film. Since dislocations in the epitaxial film cause leakage current and diffusion of electrode materials in a device, a method of reducing dislocation density has been attempted.

As one of them, for example, Japanese Patent Laid-Open No. 10-31
There is a method using selective growth as described in Japanese Patent No. 2971. In this method, patterning is performed on a substrate by using a mask material such as SiO ₂ to perform selective growth, and further, growth is continued until the mask material is buried, whereby dislocations are blocked by the mask material, and dislocation density is reduced. Is reduced.

[0004]

However, in the above method, when a mask material is embedded, a crystal grown on a mask in a lateral direction with respect to a growth surface has its crystal axis tilted as the growth proceeds (Tilt; A phenomenon called tilt occurs. Since the tilted crystals are united on the mask, a new defect is generated there. Although the cause of the tilt of the crystal axis is not clear, it is considered that the mask material has an effect.

Accordingly, an object of the present invention is to provide a growth method for obtaining a high-quality epitaxial film by reducing dislocation density without using a mask material in epitaxial growth of a GaN-based compound semiconductor crystal.

Another object of the present invention is to provide a high-quality GaN-based compound semiconductor crystal by the above growth method.

[0007]

According to the method of growing a GaN-based compound semiconductor crystal of the present invention, an anti-surfactant region is selectively formed on a substrate surface, and a GaN-based compound semiconductor crystal is formed while forming a cavity above the anti-surfactant region. Characterized by having a step of epitaxially growing.

In the method for growing a GaN-based compound semiconductor crystal according to the present invention, after forming a GaN-based compound semiconductor film on the substrate surface, an anti-surfactant region is selectively formed, and a cavity is formed above the anti-surfactant region. Alternatively, a step of epitaxially growing a GaN-based compound semiconductor crystal may be provided.

Forming the anti-surfactant region by evaporating the patterned SiO ₂ in an atmosphere containing hydrogen is one of the preferable forming methods.

[0010] A GaN-based compound semiconductor substrate of the present invention comprises a GaN compound semiconductor substrate obtained by any of the above-described methods on a substrate.
A compound semiconductor crystal, that is, an anti-surfactant region is selectively formed on the surface of the substrate directly or through a GaN compound semiconductor film,
A GaN-based compound semiconductor epitaxially grown while forming a cavity above the anti-surfactant region is provided.

[0011]

Embodiments of the present invention will be described below with reference to FIG. First, a GaN-based compound semiconductor 2 is grown on a substrate 1 in advance, and an SiO ₂ pattern 3 is formed on the surface thereof by photolithography or the like (FIG. 1A). Here, the substrate is sapphire, SiC, S
i, ZnO, spinel, or the like can be used. The pattern may have any shape, but a stripe shape is preferable because the growth rate of epitaxial growth is anisotropic.

The substrate is set in a growth apparatus and heated to a growth temperature in an atmosphere containing hydrogen. The atmosphere containing hydrogen may be a state in which hydrogen gas or a mixed gas containing hydrogen gas is flowed, or a gas containing a hydrogen group such as ammonia (NH ₃ ) is flowed, and this is thermally decomposed and hydrogen decomposed is present. It does not matter even if it is.

The SiO _{2 on the} surface of the substrate evaporates while the growth temperature is reached, and the region where the SiO ₂ pattern was
It is covered with the remaining portion 4 (FIG. 1B). In this state, GaN
When the epitaxial compound semiconductor is grown, the growth occurs from a portion not covered with the Si residual portion 4 (FIG. 1).
(C)). Reference numeral 20 denotes a grown GaN-based compound semiconductor crystal. The growth method here is preferably vapor growth, for example, metal organic chemical vapor deposition (MOCCVD) or hydride VPE (HVPE).

[0014] Si is known as an anti-surfactant material, and when covered with Si, the surface energy of the region becomes high, and the growth from there becomes difficult. If the growth is continued as it is, the GaN-based compound semiconductor crystal 20 grows so as to cover the region covered with Si (FIG. 1 (d)), and the cavity 5 is eventually formed (FIG. 1 (e)). .

Since the dislocation lines 6 extending from the underlayer are cut off by the cavities, the dislocation density on the epitaxial film surface is reduced. In addition, since no mask material is used, a phenomenon in which the crystal axis is tilted when the crystal grows in the lateral direction above the cavity does not occur, so that no new defect is generated.

In the present invention, since the anti-surfactant region is selectively formed, it is possible to control the formation position of the cavity. Therefore, if a comb-shaped electrode structure is formed above the cavity, the lower part of the electrode is substantially free from dislocation, so that diffusion of the electrode material is suppressed.

By repeating the above steps on the surface of the semiconductor crystal substrate obtained according to the present invention, the reduction of dislocations is promoted, and crystals having almost no dislocations can be obtained.

In the embodiment of the present invention, GaN is formed on a substrate.
Although the anti-surfactant region is formed on the surface of the system compound semiconductor grown in advance, the anti-surfactant region may be formed directly on the surface of the substrate.

In the embodiment of the present invention, an example in which an anti-surfactant region is obtained by evaporating SiO ₂ has been described. However, the method of forming the anti-surfactant region is not limited to this. Then, a gas containing Si, for example, SiH ₄ or tetraethylsilane is made to act thereon, and then the resist is removed to selectively form an anti-surfactant region.

In the embodiment of the present invention, an example in which Si is used as an anti-surfactant material has been described. However, similar effects can be obtained by using Mg.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments will be described below. A GaN film is grown 1.5 μm in advance on a sapphire c-plane substrate,
This was used as a base substrate. 20 thickness on GaN surface
A SiO ₂ film having a thickness of ₂ nm was deposited by sputtering, a striped pattern was formed by photolithography, and striped SiO ₂ having a width of 2 μm was obtained at intervals of 2 μm by etching. At this time, the direction of the stripe was parallel to the <1-100> direction of the underlying GaN film.

The base substrate having the SiO2 pattern formed on the surface as described above was set in a MOCVD apparatus, and a nitrogen carrier gas was flowed at 10 slm and ammonia was flowed at 5 slm. During this time, SiO
₂ evaporated, and a striped area covered with Si was obtained.

After the growth temperature was stabilized, the carrier gas was switched to hydrogen, and trimethylgallium (TMG) was further supplied at 70 μmol / min to cover the Si-covered region and grow GaN until a cavity was formed.

[0024] Measurement of the dislocation density of the thus grown GaN surface, 10 ⁷ cm ^{- 1.} From the cross-sectional TEM observation, no new defect was observed in the upper part of the cavity.

[0025]

According to the growth method of the present invention as described above, the dislocation density can be reduced without using a mask material, and a higher quality GaN-based compound semiconductor crystal can be manufactured. . If semiconductor light-emitting elements such as LEDs and LDs, light-receiving elements, and electronic devices are fabricated thereon, the characteristics thereof are expected to be dramatically improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a step of growing a GaN-based compound semiconductor crystal of the present invention.

[Explanation of symbols]

1 substrate 2 GaN-based compound semiconductor crystal 3 SiO ₂ 4 Si remaining portion 5 cavity 6 dislocation lines

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kazuyuki Tadomo 4-3 Ikejiri, Itami-shi, Hyogo Mitsubishi Cable Industries, Ltd. Itami Works F-term (reference) 5F041 AA40 CA33 CA40 CA46 CA65 CA74 5F045 AA04 AB14 AC08 AC12 AF02 AF03 AF09 AF13 CA09 CA13 DA67 DB02 DB04

Claims (4)

[Claims] A step of selectively forming an anti-surfactant region on the substrate surface and epitaxially growing a GaN-based compound semiconductor crystal while forming a cavity above the anti-surfactant region.
A method for growing an N-based compound semiconductor crystal. 2. The method of growing a GaN-based compound semiconductor crystal according to claim 1, wherein an anti-surfactant region is selectively formed after forming the GaN-based compound semiconductor film on the substrate surface. 3. The GaN-based compound semiconductor crystal according to claim 1, wherein the anti-surfactant region is formed by evaporating the patterned SiO ₂ in an atmosphere containing hydrogen. Growth method. 4. A GaN-based compound semiconductor substrate comprising a substrate and a GaN-based compound semiconductor crystal obtained by the method according to claim 1, 2 or 3.