Persistent photoconductivity in n-type GaN

We report on the spectral and temperature dependence of persistent photoconductivity (PPC) in metal-organic chemical vapor deposition grown unintentionally doped n-type GaN. The PPC effect is detectable up to temperatures of at least 352 K, the highest temperature used in this study. At 77 K, the conduction persists at a level 80% higher than the equilibrium dark conduction for over 10(4) s after removing the excitation. We have determined the spectral dependence for the optical cross section for PPC and obtain an optical ionization energy of similar to 2.7 eV. The temperature dependence of the photoconductivity decay and its nonexponential shape are explained by a distribution of capture barriers with a mean capture barrier of 0.2 eV and a width of similar to 26 meV. (C) 1997 American Institute of Physics.