Backside-illuminated HgCdTe/CdTe mosaics

This paper describes the realization of new mercury cadmium telluride (HgCdTe) detector arrays utilizing the backside-illumination design. In this approach p-type HgCdTe epilayers are grown on CdTe substrates using a liquid phase epitaxial technique. Boron ion implantation is used to form the n⁺- p junction and photodiode mosaics are produced by conventional photolithographic techniques. By varying the ratio of HgTe to CdTe in the epilayers, devices with spectral cutoffs in the range of 3 to 11 µm were fabricated and tested. For diodes with noise current limited by diffusion of minority carriers the RoA product is higher than that of a bulk device fabricated under similar conditions. This can be explained by a diffusion model based on material parameters and the geometry of n⁺- p diode structures.