High-resolution photoluminescence and reflectance spectra of homoepitaxialGaN layers

High quality homoepitaxial GaN layers grown by MOVPE on a pre-treated GaN s ingle crystal allow the measurement of photoluminescence (PL) and reflectan ce (RF) spectra with drastically improved resolution and emission intensity . For all three valence bands, at least the lowest two exciton states clear ly show up in our RF spectra. A full fit procedure based on an exciton-pola riton model including spatial dispersion allows a very precise determinatio n of the exciton energies for ideal, unstrained material. In PL, the donor (D-0,X) and acceptor (A(0),X) bound excitons exhibit linewidths of approxim ate to 100 mu eV and show an ample fine structure including two-electron tr ansitions in the case of (D-0,X).