Dependence of deep level concentrations on ammonia flow rate in n-type GaN films

Deep level transient spectroscoppy was used to characterize the deep levels of GaN films grown with various V/III ratios using metalorganic vapor phase epitaxy. Two prominent defects, located at E_C-0.569±0.003 and E_C-1.013±0.091 eV, were detected in this study. When the NH₃ flow rate was increased, we observed a slight increase in trap concentration of the E_C-0.569 eV defect and a significant increase at E_C-1.013 eV. Although a high V/III seems necessary for obtaining good quality GaN film, our results indicate that, if the ammonia is in excessive supply, it may generate a large number of E_C-1.013 eV deep level defects, which deteriorate the film quality - which should be avoided with special care.