Comparison of deep levels in GaN grown by MBE, MOCVD, and HVPE

Deep levels in n-type GaN grown by molecular beam epitaxy, metalorganic chemical vapor deposition, and hydride vapor phase epitaxy were characterized for comparison between the different methods of growth. The deep level energies, capture cross sections, and concentrations were determined for each using deep level transient spectroscopy on Schottky diodes from 80 K to 700 K, to characterize traps up to similar to 1.2 eV. The capture kinetics and bias dependence were also measured for the main traps in each, in order to determine if they are related to threading dislocations, and if they are donor-type traps. Several traps were detected in samples from each growth method. The field dependence and the capture kinetics were not the same for peaks appearing in the same temperature in deep level spectra, associated with different growth method. Traps in HVPE GaN at 0.212 eV and 0.612 eV uniquely showed field dependence indicating singly charged donors. Overall, the thick hydride vapor phase epitaxy GaN samples showed the lowest concentration of traps.