Stoichiometric and structural alterations in GaN thin films during annealling

Abstract

Annealling experiments were performed on GaN layers, grown on sapphire, over a wide range of temperatures (500-1100°C). Rutherford Backscattering Spectrometry (RBS) was performed in random and <0001> channelling geometries using 2 MeV protons and helium ions to determine the stoichiometric and structural alterations produced during annealling. We present here, for the first time, a comprehensive and quantitative analysis of the depth distribution of both stoichiometric and structural changes in the near-surface region (∼750 nm) with a resolution of 50 nm for stoichiometric and 20 nm for structural changes. No decomposition was measured for temperatures up to 800°C. Decomposition in the near-surface region increased rapidly with further increases in temperature, resulting in a near-amorphous region (500 nm) for annealling at 1100°C. We describe the range of annealling conditions under which negligible stoichiometric and structural changes are observed. Our nanoscale resolution results are useful for the fabrication and operation of conventional and nanoscale optoelectronic and high-temperature devices.