Studying C–V characteristics of MIS structures with ALD Al$_2$O$_3$ on $n$- and $p$-CdHgTe stabilized with ultra-thin native oxide

Capacitance–voltage characteristics of metal dielectric semiconductor structures with atomic layer deposition Al$_2$O$_3$ on $n$- and $p$-Cd$_{0.22}$Hg$_{0.78}$Te (with and without a surface graded-gap layer) preliminary oxidized in oxygen glow discharge plasma (with the resulting oxide thickness of 2 nm) have been studied. The obtained structures reveal the positive fixed charge with a density of $\sim$(1–6)·10$^{11}$ cm$^{-2}$. The ratio between a slow surface states density and a surface band gap width is almost independent on graded-gap layer presence, with the value of $\sim$(4–8) $\cdot$ 10$^{11}$ cm$^{-2}$ $\cdot$ eV$^{-1}$. The proposed passivation approach provides near-ideal low-frequency capacitance- voltages characterized by weak influence of fast surface states. Films of CdHgTe grown without the graded-gap surface layer are proved to be much more sensitive to the process of oxidation in glow discharge plasma.