Influence of V/III growth flux ratio on trap states in m-plane GaN grown by ammonia-based molecular beam epitaxy

Deep level transient spectroscopy (DLTS) and deep level optical spectroscopy (DLOS) were utilized to investigate the behavior of deep states in m-plane, n-type GaN grown by ammonia-based molecular beam epitaxy (NH3-MBE) as a function of systematically varied V/III growth flux ratios. Levels were detected at E-C - 0.14 eV, E-C - 0.21 eV, E-C - 0.26 eV, E-C - 0.62 eV, E-C - 0.67 eV, E-C - 2.65 eV, and E-C - 3.31 eV, with the concentrations of several traps exhibiting systematic dependencies on V/III ratio. The DLTS spectra are dominated by traps at E-C - 0.14 eV and E-C - 0.67 eV, whose concentrations decreased monotonically with increasing V/III ratio and decreasing oxygen impurity concentration, and by a trap at E-C - 0.21 eV that revealed no dependence of its concentration on growth conditions, suggestive of different physical origins. Higher concentrations of deeper trap states detected by DLOS with activation energies of E-C - 2.65 eV and E-C - 3.31 eV in each sample did not display measureable sensitivity to the intentionally varied V/III ratio, necessitating further study on reducing these deep traps through growth optimization for maximizing material quality of NH3-MBE grown m-plane GaN. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4759037]