Passivation of Hg1−xCdxTe by photochemical native oxidation: Growth characteristics

The growth of photochemical native oxides on x = 0.3 bulk wafers of n-type Hg_1−xCd_xTe has been studied with relation to growth temperature, gas flow rate, oxidizing ambient, and the wavelengths of ultraviolet radiation needed to drive the process. The growth was found to proceed with a relationship of thickness ∝ (time)^1/3 for both O₂ and N₂O ambients. An observed inverse relationship between thickness, and both growth temperature and gas flow rate, indicates a growth process that is either competing with parasitic quenching of the excited oxidizing species produced, or a diffusion controlled process, in which different growth conditions produce oxides with a variety of diffusion characteristics. The physical and optical properties of the photochemical oxides were found to be similar to anodic oxides. Rutherford backscattering spectra have shown the composition of the films to be highly dependent on growth conditions with films grown in O₂ ambients generally showing a higher mercury content than those grown in N₂O. Further, for growths in O₂ atmospheres, those carried out at lower temperatures result in more mercury in the oxide and at the oxide/mercury cadmium telluride interface when compared to those grown at higher temperatures.