The self-compensation effect of heavily Mg doped p-GaN films studied by SIMS and photoluminescence

Abstract

Abstract The electrical resistivity and compensation mechanism in heavily Mg doped p-GaN grown by metal organic chemical vapor deposition (MOCVD) are investigated. It is noted that when the Mg doping concentration is too high, the hole concentration measured by Hall test of p-GaN may decrease compared to the p-GaN samples with lower Mg doping concentration. This phenomenon suggests a possible self-compensation of Mg impurity in p-GaN. It is found that Mg concentration tested by secondary ion mass spectroscopy (SIMS) does not increase linearly when the Cp2Mg/TMGa flow rate ratio increases, and H concentration also varies with increasing Cp2Mg flow rate. The change of hole concentration may be attributed to the decrease of active acceptor (MgGa) concentration related to the self-compensation effect and the reduction of Mg incorporation rate. Actually, the integral intensity of blue luminescence (BL) caused by donor-acceptor pair (DAP) recombination in room temperature photoluminescence (PL) spectra is strengthened with increasing Cp2Mg flow rate at first, and then the BL intensity decreases when the Cp2Mg flow rate is over 100 sccm. The change of BL intensity is consistent with the conclusion that the acceptor concentration may decrease at a high Mg doping level.