Thermally induced strain in MBE grown GaN layers

A study of thermally induced strain in GaN layers grown on c-plane sapphire by molecular beam epitaxy is presented. For this, high-resolution X-ray diffraction at variable temperature (10-630 K) has been used, which is the most direct method to investigate this strain. A linear change of the lattice constant was observed for a 3 mu m thick GaN layer for temperatures above 300 K which is characterized by a thermal expansion coefficient of 3.8 x 10(-6) K-1. In contrast to this, the thermal expansion was found to be negligible for temperatures below 100 K. (C) 1998 Elsevier Science B.V. All rights reserved.