Photoreflectance study of p-type GaN layers

Abstract

Layers of GaN:Mg ∼1.5 μm thick with different concentrations of Mg dopant have been investigated by room temperature photoreflectance (PR) spectroscopy. We have compared the results obtained by the PR technique with the results obtained by standard photoluminescence (PL) and reflectance (R) techniques. We have demonstrated that PR spectroscopy is an experimental technique which is sensitive to both optical and electrical properties of investigated samples, in contrast to PL and R spectroscopies, which are only sensitive to optical properties. This feature of PR spectroscopy is very useful for investigations of GaN:Mg layers, where we have to control both optical and electrical properties. In this paper we have shown that with the increase in the number of defect states in GaN:Mg layers, associated with the increase in Mg concentration, the PR signal decreases due to the weakening of the band bending modulation. This indicates that the electrical quality of the GaN:Mg layer deteriorates with the increase in the concentration of Mg atoms.