Optical properties of thin films and quantum wells of InxGa1-xN/GaN and their dependence on laser irradiation

Abstract

We have grown bulk InxGa1-xN films and InxGa1-xN/GaN (x0.1) multiple quantum well structures on Al2O3 substrates by electron cyclotron resonance assisted molecular beam epitaxy. We have not found any signs of phase separation in bulk films with low indium content, x0.1. However, we observed inhomogeneous spatial distribution of indium with x varying from 0.1 to 0.2. In multiple quantum well structures with thin InxGa1-xN layers non-homogeneity was absent under certain growth conditions. Exposure of InxGa1-xN/GaN multiple quantum well structures to pulses of a nitrogen laser with power density I106 W cm-2 led to irreversible changes in both luminescence and reflection spectra. These results, as well as chemical analysis of irradiated surface layers performed using Auger electron spectroscopy, indicate that intensive laser irradiation decreases nitrogen content in the crystal lattice of GaN and gives rise to surface metallization.