(Invited) Deep Level Defects in AlN Studied By UV-Visible Spectroscopy

Ultraviolet-visible (UV-Vis) spectroscopy was used to measure the optical absorption and emission from high-quality, 2-inch AlN substrates grown by physical vapor transport (PVT). Spatially uniform UV absorption coefficients below 20 cm-1 at 4.68 eV (265 nm) were demonstrated. The complementary spectroscopic data were used to elucidate the mechanism of UV absorption reduction in AlN containing high levels of the carbon impurity and co-doped with Si. Formation of a carbon-silicon defect complex, which shifted the absorption deeper in the UV, was demonstrated by photoluminescence (PL) emission and PL excitation (PLE) measurements. Additional deep levels in AlN related to cation vacancy complexes with oxygen were identified and discussed.