Electrical properties of the stacked ZnS/photo-enhanced native oxide passivation for long wavelength HgCdTe photodiodes

A new surface treatment method, i.e., stacked ZnS/photo-enhanced native oxide, is proposed for HgCdTe passivation. The photo native oxide layer was deposited by direct photo chemical vapor deposition (DPCVD) using a deuterium (D/sub 2/) lamp as the optical source. By using this method, we found that there is no accumulation of Hg in the oxide/HgCdTe interface regions. Since the photo chemical vapor native oxidation is a dry oxidation method deposited at a low temperature, it can effectively suppress the Hg enhancement and the Cd depletion effects and thus obtain a high quality interface. The electrical properties of a Au-ZnS/photo-enhanced native oxide/HgCdTe metal-insulator-semiconductor (MIS) diodes were characterized by capacitance-voltage (C-V) measurement. It was found that the flat band voltage of such a MIS diode is close to 0.2 V with an effective fixed oxide charge lower than 1/spl times/10/sup 10/ cm/sup -2/.