Cathodoluminescence studies of large bulk AlN crystals

The optical properties of high quality large bulk AlN crystals have been tested by cathodoluminescence measurements carried out at different temperatures, excitation densities and electron beam energies. Both c-plane (0001) and a-plane () wafers were cut from bulk, single-crystals of AlN which were fabricated by the sublimation-recondensation technique. The wafer surfaces were subsequently prepared by chemical-mechanical polishing. The low-temperature near-band-edge cathodoluminescence spectra of a typical a-plane oriented AlN crystal show up to five transitions, which are tentatively assigned to free- and bound exciton recombination processes. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)