Photoconductivity of AlN films on SiC

The band gap and deep donor levels of bulk 6H-SiC are studied by photoconductivity and optical absorption measurements. The absorption spectrum displays two nitrogen-induced bands: one near 2 eV and another partially overlapped with the fundamental absorption of 6H-SiC at 3 eV. The low-temperature photoconductivity data reveal that the 2 eV band is due to a localized electron transition, whereas the higher-energy band involves a delocalized-electron transition from a deep center to the conduction band of the host. We also used the photoconductivity technique to estimate the band offset at the AlN/6H-SiC interface. The measured conduction and valence band offsets are 1.9 and 1.3 eV, respectively, agreeing well with our previously reported results from x-ray photoelectron spectroscopy measurements and density functional theory calculations. (c) 2005 American Institute of Physics.