Optical properties and characterization of SiC and III-V nitrides

More precise phonon energies at the positions of the conduction band minima in 4H SiC and 6H SiC have been obtained by means of high resolution 1.6K photoluminescence experiments. These experimental phonon energies have been compared with calculated values at the M,U and L points in the Brillouin zone. Erbium (Er3+) 1.54 mu m luminescence has been measured in 4H, 6H, 15R and 3C SiC from 2K to 525K. The relative integrated luminescence intensity is given from 300K to 525 K. More strikingly the relative integrated luminescence is substantially constant from 2K to 400K for the four polytypes measured. For 6H SiC, five additional higher energy spectra have been found which we attribute to higher lying Er3+ multiplets. AIN-GaN short period superlattice films have been studied by means of low temperature cathodoluminescence. Spectra are obtained at 6K, 77K and 300K. A broad, ultra-violet peak is observed above the bandgap of GaN. Evidence is given that the shift of the peak of this ultra-violet luminescence arises from quantum confinement in the GaN layers of the superlattice.