Critical points of the bandstructure of AlN/GaN superlattices investigated by spectroscopic ellipsometry and modulation spectroscopy

The ground state transition energies of AlN/GaN superlattices are determined by photoreflectance spectroscopy and spectroscopic ellipsometry. A shift of the transition energies in dependence on the barrier and well widths is found. The results are compared to quantum mechanical calculations at the Brillouin zone centre. Extending the measurements up to 9.8 eV, quantum confinement effects are observed for higher energetic critical points of the bandstructure, too. The complex dielectric functions of the superlattices are reported from 1.2 to 9.8 eV. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)