Persistent photoconductivity in n-type undoped high-resistivity GaN

Deep-level defect-related optical properties of undoped n-type high-resistivity GaN grown by metalorganic chemical vapor deposition (MOCVD) are investigated using photoluminescence (PL), photoconductivity (PC), and persistent photoconductivity (PPC) measurements. Quite interestingly, persistent photoconductivity was observed. Through the combination of our optical studied, we find that persistent photoconductivity exists in all the studied thin film. PL measurement shows a broad yellow band centered around 2.2 eV. At same time, the PC measurement also shows a 2.2 eV yellow luminescence (YL) peak. According to those experimental evidences, we believe that the commonly seen persistent photoconductivity and YL are related to each other through the same intrinsic defect. It is shown that the most probable candidate of the defect is nitrogen antisite