Admittance of MIS-Structures Based on HgCdTe with a Double-Layer CdTe/Al2O3 Insulator

Resumo

Admittance of MIS structures based on n(p)- Hg_1–xCd_xTe (at x from 0.22 to 0.40) with SiO₂/Si₃N₄, Al₂O₃, and CdTe/Al₂O₃ insulators is studied experimentally at 77 K. Growth of an intermediate CdTe layer during epitaxy results in the almost complete disappearance of the hysteresis of electrophysical characteristics of MIS structures based on graded-gap n-HgCdTe for a small range of the voltage variation. For a wide range of the voltage variation, the hysteresis of the capacitance-voltage characteristics appears for MIS structures based on n-HgCdTe with the CdTe/Al₂O₃ insulator. However, the hysteresis mechanism differs from that in case of a single-layer Al₂O₃ insulator. For MIS structures based on p-HgCdTe, introduction of an additional CdTe layer does not lead to a significant decrease of the hysteresis phenomena, which may be due to the degradation of the interface properties when mercury leaves the film as a result of low-temperature annealing changing the conductivity type of the semiconductor.