A novel method to characterize deep levels in wide-bandgap semi-insulating materials was presented. This new method combines deep level optical spectroscopy with a lighted capacitance-voltage profiling method to study the defect spectra of n-type and semi-insulating GaN co-doped with C and Si. Two prominent deep acceptor levels at EC - 2.54 and 3.28eV were found to depend strongly on C incorporation. The relationship between the concentration of these defects and C incorporation offers insight into the mechanism responsible for rendering GaN:C semi-insulating.

A Novel Method to Investigate Defect States in MBE Grown Highly Resistive GaN Doped with C and Si. A.Armstrong, A.Arehart, D.Green, J.S.Speck, U.K.Mishra, S.A.Ringel: Physica Status Solidi C, 2005, 2[7], 2411-4