High-Resolution Photoluminescence and Reflectance Spectra of Homoepitaxial GaN Layers

High quality homoepitaxial GaN layers grown by MOVPE on a pre-treated GaN single crystal allow the measurement of photoluminescence (PL) and reflectance (RF) spectra with drastically improved resolution and emission intensity. For all three valence bands, at least the lowest two exciton states clearly show up in our RF spectra. A full fit procedure based on an exciton-polariton model including spatial dispersion allows a very precise determination of the exciton energies for ideal, unstrained material. In PL, the donor (D0, X) and acceptor (A0, X) bound excitons exhibit linewidths of ≈︂100 μeV and show an ample fine structure including two-electron transitions in the case of (D0, X).