The Effect of Electrochemical Reduction and UV Exposure in H₂S Gas on Interface Properties of ZnS/p-Hg_1-xCd_xTe

A novel surface treatment method for obtaining high quality ZnS/Hg_1-xCd_xTe interface is proposed. The treatment procedure includes bromine-methanol etching, electrochemical reduction in an acetate buffer solution, and UV exposure in H₂S gas ambient inside a vacuum chamber. After the surface treatment is performed, 4500 Å-thick ZnS film is in situ evaporated on the Hg_1-xCd_xTe surface in the same chamber used for the UV treatment without exposing the surface to atmosphere. The interface properties estimated from MIS capacitors show the positive fixed interface charge density of 3×10¹⁰ cm^-2 and the insulator trap charge density of 1.8×10¹⁰ cm^-2. The interface trap density is lower than 10¹² cm^-2·eV^-1 over most of the bandgap and the minimum interface trap density is 4.5×10¹⁰ cm^-2·eV^-1 near the middle of the bandgap. The effect of each step of the surface treatment procedure is also investigated by MIS capacitors. All steps seem to be significant.