Published online by Cambridge University Press: 26 February 2011
The optical absorption in gallium nitride (GaN) films was studied by photoconductivity (PC) spectroscopy at various temperatures. At all the measured temperatures, the photoconductivity per incident photon increases with photon energy hv from 1.8 eV to 3.0 eV approximately as exp(hv/E0). Surprisingly, the measured photoconductivity tail to the infrared becomes more pronounced in magnitude at lower temperatures. We suggest from the data that the photoconductivity is dominated by majority carriers, and that the quantum efficiency η for conducting electron and hole generation by across-gap excitation increases with increasing temperature.