High-quality GaN on intentionally roughened c-sapphire

¹ Department of Materials Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
² Materials Department, University of California, Santa Barbara, CA 93106, USA
³ Department of Electrical Engineering, Technion – Israel Institute of Technology, Haifa 32000, Israel

Corresponding author: ygolan@bgumail.bgu.ac.il

Received: 15 August 2002
Revised: 24 November 2002
Accepted: 19 December 2002
Published online: 25 February 2003

Abstract

GaN films were grown using metal-organic chemical vapor deposition (MOCVD) on intentionally roughened c-sapphire in order to study the effect of the substrate roughness. Controlled substrate damage was achieved by exposing the substrate surfaces to controlled amounts of trimethylgallium followed by exposure to hydrogen at elevated temperature. The bulk film quality was studied by high-resolution X-ray diffraction and the surface topography was examined by atomic force microscopy. It was observed that mild substrate roughness (surface pit depth up to 30 nm) does not have a significant effect on the bulk film quality nor the GaN surface topography, and that recovery of the surface roughness is observed in very early stages of film growth. Cross sectional transmission electron microscopy confirmed that MOCVD GaN grown on inclined sidewalls etched in c-sapphire maintained the epitaxial relationship despite the substrate miscut of ca. 15° with respect to the c-axis.