GaN single crystal substrate and method of producing same

• US 6,413,627 B1
• Filed: 06/15/1999
• Issued: 07/02/2002
• Est. Priority Date: 06/18/1998
• Status: Expired due to Term

• Current Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Nishimoto, Tatsuya, Okahisa, Takuji, Motoki, Kensaku, Matsumoto, Naoki
• Primary Examiner(s): Le, Hoa T.
• Application Number:
  US09/333,879
• Time in Patent Office: 1,113 Days
• Field of Search: 428/323, 428/328, 428/402, 428/332, 423/409, 117/952
• US Class Current: 428/332
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 29/406 Gallium nitride
• CPC Class Codes: C30B 29/60 characterised by shape
• CPC Class Codes: H01L 21/02395 Arsenides
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD
• CPC Class Codes: H01L 21/02639 Preparation of substrate for selective deposition
• CPC Class Codes: H01L 21/02647 Lateral overgrowth
• CPC Class Codes: H01L 21/02664 Aftertreatments planarisation in general H01L21/304
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: Y10T 428/26 Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension

Abstract

A freestanding GaN single crystal substrate is made by the steps of preparing a (111) GaAs single crystal substrate, forming a mask having periodically arranged windows on the (111) GaAs substrate, making thin GaN buffer layers on the GaAs substrate in the windows of the mask, growing a GaN epitaxial layer on the buffer layers and the mask by an HVPE or an MOC, eliminating the GaAs substrate and the mask away and obtaining a freestanding GaN single crystal substrate. The GaN single crystal has a diameter larger than 20 mm and a thickness more than 0.07 mm, being freestanding and substantially distortion-free.

Claims

1. A GaN single crystal substrate having a diameter longer than 20 mm, a thickness more than 0.07 mm and being freestanding.

2. A GaN single crystal substrate as claimed in claim 1, wherein the GaN substrate is colorless and transparent.

3. A GaN single crystal substrate as claimed in claim 1, wherein the GaN substrate is transparent but yellowish, brownish or grayish.

4. A GaN single crystal substrate as claimed in claim 1, wherein an absorption coefficient for light is less than 120 cm⁻

1 for a wavelength range between 400 nm and 600 nm.

5. A GaN single crystal substrate as claimed in claim 1, wherein intrinsic internal stress is less than 7 MPa.

6. A GaN single crystal substrate as claimed in claim 1, wherein a curvature radius of distortion is more than 600 mm.

7. A GaN single crystal substrate as claimed in claim 1, wherein a distortion height at a center of the substrate is less than 0.55 mm for a 2 inch diameter.

8. A GaN single crystal substrate as claimed in claim 1, wherein a concentration of As is less than 10¹⁷ cm⁻

3.

9. A GaN single crystal substrate as claimed in claim 1, wherein the GaN substrate substantially does not include carbon.

10. A GaN single crystal substrate as claimed in claim 1, wherein the GaN substrate has a top surface and a bottom surface, and one or both of them are polished.

11. A GaN single crystal substrate as claimed in claim 10, wherein normals on low index planes of GaN crystals nearly parallel to the surface of the GaN substrate incline at an angle less than 3 degrees to a normal on the substrate surface.

12. A GaN single crystal substrate as claimed in claim 11, wherein fluctuation of normals of low index planes of GaN crystals nearly parallel to the surface of the GaN substrate is less than 4 degrees.

13. A GaN single crystal substrate as claimed in claim 10, wherein a distortion height of the GaN after being polished is less than 200 μ

m for 2-inch diameter.

14. A GaN single crystal substrate as claimed in claim 10, wherein the surface is a GaN(0001) plane.