BASE SUBSTRATE, GALLIUM NITRIDE CRYSTAL MULTI-LAYER SUBSTRATE AND PRODUCTION PROCESS THEREFOR

• US 20130313567A1
• Filed: 03/02/2012
• Published: 11/28/2013
• Est. Priority Date: 03/07/2011
• Status: Abandoned Application

• Current Assignee: Tokuyama Corporation, Yamaguchi University
• Original Assignee: Tokuyama Corporation, Yamaguchi University
• Inventors: Azuma, Masanobu, Tadatomo, Kazuyuki, Furuya, Hiroshi, Okada, Narihito
• Application Number:
  US13/983,257
• Publication Number:
  US 20130313567A1
• Time in Patent Office: Days
• US Class Current: 257/76
• CPC Class Codes: C30B 29/406 Gallium nitride
• CPC Class Codes: H01L 21/0242 Crystalline insulating materials
• CPC Class Codes: H01L 21/0243 Surface structure
• CPC Class Codes: H01L 21/02433 Crystal orientation
• 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 21/0265 Pendeoepitaxy
• CPC Class Codes: H01L 29/2003 Nitride compounds
• CPC Class Codes: H01S 2304/12 Pendeo epitaxial lateral overgrowth [ELOG], e.g. for growing GaN based blue laser diodes
• CPC Class Codes: Y10T 428/2457 Parallel ribs and/or grooves

Abstract

A GaN crystal multi-layer substrate having surfaces with various crystal orientations formed on a sapphire base substrate, such as a substrate whose principal surface is a <11-20> plane which is the a-plane, a <1-100> plane which is the m-plane, or a <11-22> plane having a low threading dislocation density and high crystal quality of a GaN crystal, and a production process therefor.

The gallium nitride crystal multi-layer substrate comprises a sapphire base substrate and a gallium nitride crystal layer which is formed on the substrate by crystal growth, wherein the gallium nitride crystal layer is formed by lateral crystal growth from sidewalls which are c-planes of a plurality of grooves formed in the principal surface of the sapphire base substrate in such a manner that the surface thereof is parallel to the principal surface of the base substrate and constituted of a nonpolar a-plane or m-plane or a semipolar <11-22> plane, and the dark-spot density of the gallium nitride crystal is less than 2×10⁸/cm², preferably not more than 1.85×10⁸/cm², particularly preferably not more than 1.4×10⁸/cm².

Claims

1. A gallium nitride crystal multi-layer substrate comprising a sapphire base substrate and a gallium nitride crystal layer which is firmed by crystal growth on the substrate, wherein

the gallium nitride crystal layer is formed by lateral crystal growth from the sidewalls of a plurality of grooves formed in the principal surface of the sapphire base substrate in such a manner that the surface thereof is parallel to the principal surface, and the dark-spot density of the gallium nitride crystal is less than 2×

10⁸/cm².

2. The gallium nitride crystal multi-layer substrate according to claim 1, wherein the dark-spot density of the gallium nitride crystal is not more than 1.4×

10⁸/cm².

3. The gallium nitride crystal multi-layer substrate according to claim 1, wherein the gallium nitride crystal layer has a surface with a nonpolar or semipolar orientation.

4. The gallium nitride crystal multi-layer substrate according to claim 1, wherein the sidewalls which are the starting points of lateral crystal growth are each the c-plane of a sapphire single crystal.

11. The gallium nitride crystal multi-layer substrate according to claim 2, wherein the gallium nitride crystal layer has a surface with a nonpolar or semipolar orientation.

12. The gallium nitride crystal multi-layer substrate according to claim 2, wherein the sidewalls which are the starting points of lateral crystal growth are each the c-plane of a sapphire single crystal.

13. The gallium nitride crystal multi-layer substrate according to claim 3, wherein the sidewalls which are the starting points of lateral crystal growth are each the c-plane of a sapphire single crystal.

5. A process for manufacturing a gallium nitride crystal multi-layer substrate, comprising the steps of:

forming a plurality of grooves, each having sidewalls inclined with respect to the principal surface of a sapphire base substrate, in the sapphire base substrate; and

laterally growing a gallium nitride crystal selectively from the sidewalls of the grooves, wherein

the width (d) of an area for growing a gallium nitride crystal on the sidewalls is set to 10 to 750 nm.

6. The process for manufacturing a gallium nitride crystal multi-layer substrate according to claim 5, wherein the width (d) of the area for growing a gallium nitride crystal is 100 to 200 nm.

7. The process for manufacturing a gallium nitride crystal multi-layer substrate according to claim 5, wherein the sidewalls which are the starting points of lateral crystal growth are each the c-plane of a sapphire single crystal.

14. The process for manufacturing a gallium nitride crystal multi-layer substrate according to claim 6, wherein the sidewalls which are the starting points of lateral crystal growth are each the c-plane of a sapphire single crystal.

8. A sapphire base substrate for manufacturing a crystal multi-layer substrate, wherein the sapphire base substrate has a plurality of grooves, each having sidewalls inclined with respect to the principal surface thereof, and the width (d) of an area for growing a gallium nitride crystal selectively on the sidewalls of the grooves is set to 10 to 750 nm.

9. The sapphire base substrate for manufacturing a crystal multi-layer substrate according to claim 8, wherein the width (d) of the area for growing a gallium nitride crystal is 100 to 200 nm.

10. The sapphire base substrate for manufacturing a crystal multi-layer substrate according to claim 8, wherein the sidewalls which are the starting points of lateral crystal growth are each the c-plane of a sapphire single crystal.

15. The sapphire base substrate for manufacturing a crystal multi-layer substrate according to claim 9, wherein the sidewalls which are the starting points of lateral crystal growth are each the c-plane of a sapphire single crystal.