For the first time, SiO2layers, 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 SiO2films, grown at 60 °C and 0.5 Torr for a mixture of SiH4and 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 SiO2thin films. The electrical properties of these SiO2layers were investigated by performing high frequency (1 MHz) capacitance–voltage (C–V) and current–voltage (I–V) measurements, at 77 K. TheC–Vmeasurement shows that the minimum interface state density is 5×1010cm−2 eV−1with a hysteresis smaller than 0.2 V. The maximum dielectric strength observed fromI–Vmeasurement is around 580 kV/cm.