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

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 0.700.25eV. 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. Display Omitted The band alignment of Ta2O5/GaN has been measured experimentally.The HCl treated GaN surface showed the lowest oxygen and carbon contamination.Ta2O5 films of thicknesses up to 10nm were deposited by RF magnetron sputtering.The valence band offset was calculated to be 0.700.25eV using Kraut's method.The band gaps were found by ellipsometry: 3.34eV for GaN and 4.4eV for Ta2O5.