Effect of nitrogen plasma power on defect levels in Ni/n-GaN Schottky diodes grown by molecular beam epitaxy

Abstract

The incorporation of deep level defects in n-type GaN grown by plasma assisted molecular beam epitaxy was studied via systematic adjustment of the nitrogen plasma source power from 150 to 400 W while maintaining a constant V/III beam flux ratio. Deep level optical spectroscopy and conventional thermal deep level transient spectroscopy measurements, which together enable deep level detection throughout the GaN band gap, revealed several deep level concentrations that depend strongly on rf-plasma power. The concentrations of the gallium vacancy deep level at EC-2.60 eV and carbon-related point defects with energy levels at EC-3.28 and EC-1.35 eV are found to be very sensitive to the nitrogen source power, increasing by up to 50 times for a corresponding increase in plasma power from 150 to 400 W. The relation between the concentrations of these traps and plasma power follows an Arrhenius-type behavior and is suggestive of plasma damage associated with the energetics of the constituent active nitrogen species. In contrast, two traps at EC-0.86 and EC-0.59 eV did not exhibit a systematic dependence on plasma power, with this difference a result of the dislocation-related nature of these defects.