Deep-level transient spectroscopy of HVPE grown n-GaN revealed 3 dominant traps below the conduction band, commonly associated with HVPE-grown material. It was found here that the concentration of the Ec-0.61eV level was dependent on the biasing conditions: zero bias annealing at 370K decreases the concentration of the 0.61eV level to a non-zero value, while reverse bias annealing increases the concentration within the region probed. The change in the defect concentration became lower for thicker GaN layers with a lower density of threading dislocations. This behavior was tentatively attributed to the neutralization of the 0.61eV level by a mobile defect species, which was associated with dislocations present in the material.

Bias-Dependent Deep Level in HVPE n-GaN. L.Wu, W.E.Meyer, F.D.Auret, M.Hayes: Physica B, 2003, 340-342, 475-8