Effects of anodic fluoro‐oxide on the thermal stability of Hg1−xCdxTe photoconductive arrays

Hg1−xCdxTe (x∼0.2) photoconductive arrays passivated with anodic fluoro‐oxides show an improved thermal stability relative to arrays fabricated with anodic oxides. The performance of the photoconductors with the anodic fluoro‐oxide is only slightly degraded by annealing at temperatures up to 100–105 °C, in contrast to the monotonic decrease observed in arrays passivated with an anodic oxide caused by annealing above 70 °C. The improved stability of the fluoro‐oxides does not depend much on the bath composition, as long as it is a solution of hydroxyl and fluoride ions. Both secondary ion mass spectroscopy and low‐energy proton induced nuclear reaction, which is very sensitive to fluorine atoms, were used as depth profile probes. It was found that the fluorine concentrated at the anodic film–semiconductor interface as well as on the film surface. A mechanism by which fluorine is deposited in such a manner is advanced.