Interface of p-type Hg1−xCdxTe passivated with native sulfides

Abstract

The process for forming native sulfide films on p-type Hg1−xCdxTe with x≂0.2–0.3 by anodic sulfidization is described and studied. The analytical, optical, and electrical properties of the resulting interface are reported. The results of Auger electron spectroscopy analysis indicate that homogeneous CdS films with an abrupt interfacial transition are formed on Hg1−xCdxTe with x=0.215–0.290. The measured dispersion of the index of refraction and the dielectric constant of the native sulfide films are consistent with the reported data for bulk CdS. The interface between Hg1−xCdxTe and its native sulfide in combination with deposited ZnS has excellent electrical properties. A low fixed surface state density of the order of Nss ≂5×1010 cm−2, a low concentration of fast surface state density of the order of 5×109 cm−2 eV−1, and a small amount of trapping effects in the sulfide are observed. The MIS capacitors exhibit thermal stability up to 95 °C anneal in vacuum. The main features of the interface of p-HgCdTe utilizing native sulfides are the low fixed surface states and the practically flatband conditions which are imposed for a wide range of composition x and doping level of the substrates. It contrasts with the high fixed positive surface-state density which is observed on interfaces utilizing native oxides of HgCdTe and which invariably invert the surfaces of p-Hg1−xCdxTe. The properties of the interface between Hg1−xCdxTe and its native sulfide suggest potential applications for improving the surface passivation of photovoltaic diodes implemented on p-type Hg1−xCdxTe.