Free-carrier effects in gallium nitride epilayers: Valence-band dispersion- art. no. 081203

The dispersion of the A-valence-band in GaN has been deduced from the obser vation of high-index magnetoexcitonic states in polarized interband magneto reflectivity and is found to be strongly nonparabolic with a mass in the ra nge 1.2-1.8m(e). It matches the theory of Kim et al. [Phys. Rev. B 56, 7363 (1997)] extremely well, which also gives a strong k-dependent A-valence-ba nd mass. A strong phonon coupling leads to quenching of the observed transi tions at about an LO-phonon energy above the band gap and a strong nonparab olicity. The valence band was deduced from subtracting from the reduced dis persion the electron contribution with a model that includes a full treatme nt of the electron-phonon interaction.