Effect of HgCdTe native oxide on the electro-physical properties of metal–insulator–semiconductor structures with atomic layer deposited Al2O3

Abstract

Metal–insulator–semiconductor structures with atomic layer deposited (ALD) Al2O3 and ultra-thin native oxide were formed on n-type variband Hg1–xCdxTe of two different volume compositions x, referred to as MWIR and LWIR. It is shown that presence of native oxide prior to plasma-enchanced ALD process and origination of this oxide are crucial to properties of an insulator–semiconductor interface. Ultra-thin native oxide formed in glow discharge or remote RF plasma is much more stable than oxide formed during storage of sample in air and provides significantly improved interface quality. The positive sign of fixed charge introduced by plasma oxide is more preferable for an n-type semiconductor than the negative one, but obtained density of fixed charge up to 1 × 1012 cm−2 is still quite high and should be reduced. Density of slow surface states, being responsible for hysteresis of C–V characteristics, is much lower in case of plasma oxide, with C–V curves showing near-ideal high-frequency behavior.