Abstract
A mercury cadmium telluride (MCT) surface subjected to different processing steps of polishing, chemical and electrochemical etching has been examined using x-ray diffraction (XRD). The presence of several oxide phases as well as the elemental tellurium on the substrate surface has been revealed. It is shown that a combination of chemical and in situ electrochemical etching can effectively remove the defective layer containing the oxides as well as the surface tellurium. Cadmium sulfide films grown by a chemical deposition route have been investigated as a passivant for mercury cadmium telluride. The CdS films have been characterized using optical and x-ray diffraction techniques. Frequency-dependent low temperature capacitance measurements of the Au/Hg1-xCdxTe/CdS/Au structure have been used to investigate the electrical properties of the interface. It is shown that the in situ electrochemical etching prior to passivation results in the fabrication of metal-insulator semiconductor (MIS) devices with low fast and slow surface state density and negligible hysteresis.