Passivation with SiO2 on HgCdTe by direct photochemical-vapor deposition*

Abstract

For the first time, SiO2 layers, prepared by direct photochemical-vapor deposition, were passivated onto HgCdTe substrates using a deuterium (D2) lamp as the ultraviolet and vacuum-ultraviolet light source. It was found that the refractive index of the SiO2 films, grown at 60 °C and 0.5 Torr for a mixture of SiH4 and O2, is close to 1.462 (the refractive index of thermal silicon dioxide) when the gas ratio (SiH4/O2) is adjusted to 0.2. Various characterization techniques, such as x-ray photoemission, Auger-electron, and Fourier-transform spectroscopies were used to give a detailed study of the physical and chemical properties of the SiO2 thin films. The electrical properties of these SiO2 layers were investigated by performing high frequency (1 MHz) capacitance–voltage (C–V) and current–voltage (I–V) measurements, at 77 K. The C–V measurement shows that the minimum interface state density is 5×1010 cm−2 eV−1 with a hysteresis smaller than 0.2 V. The maximum dielectric strength observed from I–V measurement is around 580 kV/cm.