THERMALLY-INDUCED STRAIN IN MBE GROWN GAN LAYERS

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