Simultaneous impurity-band and interface conduction in depth-profiled n-GaN epilayers

Abstract

We report on temperature-dependent differential Hall-effect and resistivity measurements, between 10 and 300 K, on two Si-doped GaN epitaxial layers grown by MOCVD on sapphire substrates. These experiments indicate parallel conduction paths in our layers, while depth profiling using plasma-etching shows that two paths are simultaneously present: an impurity band in the Si-doped region and a conducting layer at the GaN/sapphire interface.