Effects of NO annealing and GaOxNy interlayer on GaN metal-insulator-semiconductor capacitor with SiO2 gate dielectric

Abstract

SiO2 was deposited on GaN by radio-frequency sputtering to fabricate metal-insulator-semiconductor (MIS) capacitors. Before the deposition, an ultrathin GaOx Ny interlayer was thermally grown on the GaN wafer to improve the quality of the insulator/ GaN interface. The interface-trap density at 0.4 eV below the conduction bandedge was reduced by one order compared with that of a sample without the GaOx Ny interlayer. Annealing in NO gas at 800°C was conducted on both samples, and turned out to greatly suppress their oxide charges. The NO -annealed sample with the GaOx Ny interlayer achieved the lowest oxide-charge density of 1.7× 1011 cm-2, as compared to 9.5× 1011 cm-2 for its counterpart without the GaOx Ny interlayer and about 8.0× 1012 cm-2 for the two nonannealed samples. Moreover, the NO annealing was found to effectively reduce border traps. Secondary-ion mass spectrometry analysis was performed to explain how the GaOx Ny interlayer and NO annealing affect the performance of the GaN MIS capacitors. © 2007 The Electrochemical Society.