Refractive indices of zincblende structure β-GaN(001) in the subband-gap region (0.7–3.3 eV)

Abstract

Refractive indices n and absorption coefficients α of epitaxial metastable zincblende structure β-GaN(001) were determined over the subband-gap energy range between 0.8–3.1 eV from an analysis of optical transmission spectra. n was found to vary from 2.25 to 0.8 eV (1.55 μm) to 2.50 at 3.1 eV (0.4 μm) with an energy E (eV) dependence that is well described by a Sellmeir-type dispersion relationship, n2(E)=1+148/(38.3−E2). The refractive indices of β-GaN are 3%–4% smaller than previously reported values for hexagonal α-GaN.