Effect of Wafer Off-Angles on Defect Formation in Drift Layers Grown on Free-Standing GaN Substrates

The effect of the surface off-angle toward either the a- or m-axis on the defect formation is characterized using deep-level transient spectroscopy (DLTS) in conjunction with the carrier concentration for Ni Schottky contacts formed on n-GaN drift layers. In both noncontact and conventional capacitance-voltage results, off-angle dependence on carrier concentration is observed. For all samples, a large dominant peak appears at approximately 270 K in the DLTS spectra and is attributed to E3 (E-C - 0.57-0.61 eV) defects. Carbon atoms can act as carrier compensators and form E3 defects. These results can be interpreted based on how C incorporation during crystal growth depends on the off-angle.