Lattice Paramjz Tizrs of Gallium Nitride at High Temperatures and Resulting Epitaxial Misfits with Alumina and Silicon Carbide Substrates

Lattice constants of single phase gallium nitride were measured from room temperature to 1273 IS using high temperature x-ray powder diffraction. The data were used to calculate the epitaxial misfits using the epitaxial relationships, GaN(OOOl)]]A.1203(OO01) and GaN[10i0]]]A120s[1 1201 and GaN(OOOl#iH-SiC(OOO1) and GaN[lOiO]]]6H-SiC[lOiO], reported in the literature. Using the above relationships epitaxial misfits of 13.62 % and -3.57% were calculated between GaN and Al203 and between GaN and 6H-Sic, respectively, at 1273 K. From these epitaxial misfits, layer strains of -0.22% and 0.16%, respectively, were calculated for cooling from 1273 K to room temperature. INTRODUCTION Gallium nitride (GaN), with a direct band gap of 3.4 eV [l], is a promising material in the development of short-wavelength light emitting devices [2,3]. Other optical device applications for GaN include semiconductor lasers and optical detectors. The crystal structure of GaN was first reported by Juza and Hahn [4]. GaN crystallizes in the hexagonal crystal system and the xray powder diffraction pattern was indexed using space group P6qnc (186) [4]. Balkas et al. [5] gave an indexed powder pattern and refined lattice parameters of a = 3.18907(8) and c = 5.1855(2) A. It has recently become possible to grow epitaxial fihns of GaN on various substrates by the Copyright(c)JCPDS-International Centre for Diffraction Data 2000,Advances in X-ray Analysis,Vol.43 338