XPS investigation of the ALD Al2O3/HgCdTe heterointerface

Abstract

Metal-insulator-semiconductor (MIS) structures were fabricated on n-type variband HgCdTe with Al2O3 deposited by plasma-enhanced ALD. Early stages of the deposition process performed at 120 °C were studied by means of XPS for the first time. Partial decomposition and conversion of HgCdTe native oxide presented on the surface were observed as well as mercury atoms out-diffusion from the near-surface region. The width of alumina band gap and the offsets of Al2O3/HgCdTe bands were determined. Capacitance-voltage characteristics reveal a negative fixed charge with the density of ∼1 × 1012 cm-2 and wide hysteresis depending on the voltage sweep range. An additional intermediate layer lowering an apparent permittivity value of the MIS insulator layer is found. By varying the thickness of the insulator of the samples, the permittivity of Al2O3 was extracted to be 7.6. The estimated Al2O3 properties correspond to the oxygen-deficient amorphous phase of alumina.