SiO2deposited photochemically at a substrate temperature of 100 °C has been evaluated as a surface passivant on Hg1−xCdxTe  (x=0.30). It has been determined that the electrical properties of the (Hg, Cd)Te–SiO2interface are dependent on the pretreatment given the semiconductor surface prior to the insulator deposition. Formation of a thin native oxide on the (Hg, Cd)Te surface during the pretreatment appears to enhance the resultant (Hg, Cd)Te–SiO2interface properties. A significant spread in the (Hg, Cd)Te–SiO2interface properties is observed, likely owing to the nature of how this native oxide forms and interactions between the native oxide and the SiH4in the photochemical reactor. It is shown through neutron activation analysis that the Hg employed as a photochemical sensitizer is incorporated in the SiO2at a concentration of 1.8 ppm.