Experimental band alignment of Ta₂O₅/GaN for MIS-HEMT applications

Abstract

The band alignment of Ta2O5/GaN has been measured experimentally. The HCl cleaning has been found to be effective in removing oxygen from the GaN surface and was used prior to deposition of the Ta2O5 films by radio frequency magnetron sputtering. Variable angle spectroscopic ellipsometry was performed to measure the thickness, optical constants and band gap of GaN and Ta2O5/GaN samples. The valence band offset of Ta2O5/GaN was measured by X-ray photoelectron spectroscopy using Kraut's method, and found to be 0.70 ± 0.25 eV. The results provide experimental evidence of an earlier theoretical study of higher effective barrier for holes than for electrons in the Ta2O5/GaN material system