The interface of plasma-anodized Hg1−xCdxTe

Abstract

The process for forming plasma-anodized oxide on Hg1−xCdxTe with x = 0.215 and 0.290 and the properties of the interface are studied. The results of Auger electron spectroscopy and x-ray photoelectron spectroscopy surface analytical characterization and the electrical interface characterization are compared with respective data on the interface between Hg1−xCdxTe and its solution anodized native oxide. The plasma oxide exhibits a decreasing gradient of oxygen and an increasing gradient of unoxidized tellurium from the surface towards the bulk semiconductor. An accumulation of fluorine at the interface unique to the plasma oxide is observed. Metal-Insulator-Semiconductor (MIS) devices with the plasma-anodized interface have a relatively low concentration of positive fixed surface charge density, (1–3)×1011 cm−2, and fast surface state density per unit band gap of about 2×1011 cm−2 eV−1, measured at 77 K. The hysteresis in the capacitance-voltage characteristics of the MIS devices is negligible, indicating the near absence of slow-trapping effects which have been observed in anodic solution oxides. Photoconductors passivated with plasma oxide exhibit good responsivity and detectivity, indicating small surface recombination velocity and small interface trapping. A significant advantage of the plasma oxide is the excellent thermal stability of the interface. Devices such as MIS capacitors and photoconductors may be annealed in vacuum up to 95 °C for prolonged periods while retaining their properties.