Correlation between Ga-O signature and midgap states at the Al2O3/In0.53Ga0.47As interface

Al2O3/In0.53Ga0.47As gate stacks were fabricated using different concentrations of NH4OH as a pre-deposition treatment. Increased NH4OH concentrations significantly reduced the C-V weak inversion hump and the measured near midgap interface states density (Dit). X-ray photoelectron spectroscopy (XPS) studies revealed that these changes in the electrical properties were accompanied by a reduction in the amount of the Ga-O bonding while As-As dimers as well as other XPS detected InGaAs surface species did not correlate with the observed Dit trend. Possible explanations for these findings are suggested.