GaN single-crystal substrate, nitride type semiconductor epitaxial substrate, nitride type semiconductor device, and methods of making the same

a technology of nitride type semiconductor and substrate, which is applied in the direction of crystal growth process, monocrystalline material growth, semiconductor laser, etc., can solve the problems of difficult to achieve a suitable flatness of mechanically polished substrate, difficult to yield a flat surface, and chemically unstable single crystal substrate, etc., to achieve improved flatness of heterojunction interface, improve the effect of current amplification factor and favorable crystallinity

Inactive Publication Date: 2005-05-05
SUMITOMO ELECTRIC IND LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Benefits of technology

[0008] However, the conventional GaN substrate mentioned above may be problematic as follows: Namely, while it is necessary for the surface of the prepared GaN single-crystal substrate to be mechanically polished flat in order to form an epitaxial layer thereon, the GaN single-crystal substrate is chemically so unstable that it is hard to polish by chemical mechanical polishing (CMP) which is used for other semiconductor substrates. Therefore, it is difficult for the mechanically polished substrate to attain a flatness suitable for epitaxial growth, whereby the substrate surface after typical mechanical polishing has an Rms (root-mean-square roughness) of about 1.0 nm. When an epitaxial layer is formed on a substrate having such a rough surface, three-dimensional growth occurs due to the random nucleus generation in uneven parts, which makes it difficult to yield a flat surface. Also, when grown nuclei generated are combined together in such a growth mode, crystal defects such as dislocations are likely to occur due to directional shifts existing among the nuclei, which deteriorates crystallinity. Namely, for making a semiconductor apparatus having a better quality on a GaN single-crystal substrate, it is necessary to eliminate the defects (e.g., damages and distortions) occurring due to the surface processing.

Problems solved by technology

However, the conventional GaN substrate mentioned above may be problematic as follows: Namely, while it is necessary for the surface of the prepared GaN single-crystal substrate to be mechanically polished flat in order to form an epitaxial layer thereon, the GaN single-crystal substrate is chemically so unstable that it is hard to polish by chemical mechanical polishing (CMP) which is used for other semiconductor substrates.
Therefore, it is difficult for the mechanically polished substrate to attain a flatness suitable for epitaxial growth, whereby the substrate surface after typical mechanical polishing has an Rms (root-mean-square roughness) of about 1.0 nm.
When an epitaxial layer is formed on a substrate having such a rough surface, three-dimensional growth occurs due to the random nucleus generation in uneven parts, which makes it difficult to yield a flat surface.
Also, when grown nuclei generated are combined together in such a growth mode, crystal defects such as dislocations are likely to occur due to directional shifts existing among the nuclei, which deteriorates crystallinity.

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  • GaN single-crystal substrate, nitride type semiconductor epitaxial substrate, nitride type semiconductor device, and methods of making the same
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  • GaN single-crystal substrate, nitride type semiconductor epitaxial substrate, nitride type semiconductor device, and methods of making the same

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[0071] A growth method employed for epitaxial growth can be selected from OMVPE, HVPE, MBE, and the like. When any of them is chosen, the GaN single-crystal substrate 11 is heat-treated within an apparatus for growth and then, without taking out the GaN single-crystal substrate 11, the nitride type compound semiconductor layer 12 is epitaxially grown thereon, whereby the surface of the substrate 11 is kept from being contaminated. Therefore, the surface processing step required when the surface is oxidized or contaminated is unnecessary, whereby a high-quality epitaxial substrate can be made easily.

[0072] The GaN substrate 11 was heat-treated in an OMVPE apparatus under various conditions. Further, the GaN layer 12 was epitaxially grown within the same apparatus. As shown in FIG. 5, the OMVPE apparatus 20 used comprises a vertical growth furnace (reaction chamber) 22 constructed so as to jet out material gases at right angles with respect to the surface of the substrate 11. The gro...

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Abstract

The GaN single-crystal substrate 11 in accordance with the present invention has a polished surface subjected to heat treatment for at least 10 minutes at a substrate temperature of at least 1020° C. in a mixed gas atmosphere containing at least an NH3 gas. As a consequence, an atomic rearrangement is effected in the surface of the substrate 11 in which a large number of minute defects are formed by polishing, so as to flatten the surface of the substrate 11. Therefore, the surface of an epitaxial layer 12 formed on the substrate 11 can be made flat.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a GaN single-crystal substrate, a nitride type semiconductor epitaxial substrate, a nitride type semiconductor device, and methods of making them for use in light-emitting devices and the like. [0003] 2. Related Background Art [0004] Attention has recently been given to light-emitting devices using nitride type compound semiconductors, since they can emit light having a short wavelength in a region from ultraviolet to blue-green. These devices such as light-emitting diodes and laser diodes are prospective as illumination and display apparatus, or light sources for next-generation DVD. As a substrate for use in these light-emitting devices, a GaN single-crystal substrate having a lattice constant identical to that of a GaN layer, which is a major nitride type semiconductor layer, is preferably employed. However, it has conventionally been considered difficult to make a GaN single-crys...

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Application Information

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Patent Type & AuthorityApplications(United States)
IPC IPC(8): C30B25/02H01L21/20H01L21/205C30B29/38H01L33/32H01S5/323
CPCC30B25/02C30B29/403C30B29/406H01L21/3247H01L21/0254H01L21/02658H01L21/3245H01L21/02389
InventorUENO, MASAKITAKASUKA, EIRYOCHUA, SOO-JINCHEN, PENG
OwnerSUMITOMO ELECTRIC IND LTD