The interface between Hg 1− xCd xTe and its native oxide

Abstract

The results of a study of the electrical properties of the interface between Hg 1− x Cd x Te with x = 0.21 and its native oxide at 77°K are presented. The native oxide is formed by anodic oxidation and results in an interface with reproducible properties. The surface charge, the surface mobility and the effective lifetime are obtained from galvanomagnetic measurements and are related to the semiconductor bulk parameters, the oxide thickness and the annealing conditions. The surface state charge and the metal-semiconductors work function difference are obtained from the shift of the flat band voltage of metal-oxide-semiconductor (MOS) capacitor characteristics. The interface between Hg 1− x Cd x Te and its native anodic oxide is characterized by a density of fast surface states of the order of 5 × 10 11cm −2 (eV −1) near the middle of the bandgap. The density of states increases towards the band edges to the order of 10 13cm −2 (eV −1). The measured flat band voltage is approximately −0.5 V for an oxide thickness of 500 Å and for an n-type semiconductor with an electron carrier concentration in the range 1–3 × 10 15 cm −3 at 77°K. The fixed oxide surface state charge is positive for both p-type and n-type semiconductors and is of the order of 6 × 10 11 charges per cm −2. The surface properties, the significance and the reproducibility of the results are evaluated.