Bias-dependent deep level in HVPE n-GaN

Deep-level transient spectroscopy (DLTS) on HVPE grown n-GaN revealed three dominant traps below the conduction band, commonly associated with HVPE-grown material. In this study, it was found that the concentration of the E-C-0.61 eV level is dependent on the biasing conditions: zero bias annealing at 370 K decreases the concentration of the 0.61 eV level to a non-zero value, while reverse bias annealing increases the concentration within the region probed. The change in the defect concentration becomes lower for thicker GaN layers with a lower density of threading dislocations. We tentatively ascribe this behaviour to the neutralisation of the 0.61 eV level by a mobile defect species, which is associated with dislocations present in the material. (C) 2003 Elsevier B.V. All rights reserved.