Transient behaviours of yellow and blue luminescence bands in unintentionally doped GaN

Yellow Luminescence (YL) band and blue luminescence (BL) band in a studied unintentionally doped GaN sample show a transient behaviour where the observed luminescence intensities change with the exposure time of the sample under 325 nm laser beam excitation at 10-300 K. Such an intensity variation is accompanied with a red-shift for YL peak at 10-140 K and one for BL peak at 140 K. We propose that such behaviours are related to the chemical transformations of YL-related C_N and C_NO_N defects, and BL-related C_N-H_i and C_NO_N-H_i defects during the exposure.