Structural investigations of GaN films with X‐ray standing waves

Abstract

AbstractThe technique of X‐ray standing waves (XSW) was applied for the first time to thick undoped GaN films grown on (0001) sapphire substrates. The film polarity was determined unambiguously in (006) backscattering geometry, which proves the feasibility of XSW measurements on this system. Reflectivity measurements yielded a significant decrease of the crystal quality already at a Mg dopant concentration as low as 4 × 1018cm–3. For a Mg dopant concentration of (3‐4)×1019cm–3, crystallites with a difference in the lattice constant of Δc/c = 0.51‰ are found, which impedes XSW investigations on thick doped crystals. In order to solve this problem, we propose a modified sample structure, consisting of a thin doped layer on top of a thick undoped GaN film. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)