Planar double-layer heterojunction HgCdTe photodiodes and methods for fabricating same

摘要

A double layer heterojunction array 10 of IR photodiodes has formed within an upper planar surface region of a collector layer 16 a plurality of isolation junctions 20 which are disposed between individual photodiodes. The isolation junctions are formed by a thermally driven process of type-converting the p-type or n-type collector layer to the opposite type of material. This type conversion forms p-n homojunctions at the edges of the isolation junctions which isolate the individual photodiodes one from another. The type-conversion process of the invention provides two isotype junctions which together reflect excess minority charge carriers away from the surface of the device as well as from neighboring photodiodes. One method of the invention discloses the selective annealing of the surface of an n-type collector layer to extract mercury atoms thereby creating mercury vacancies which act as acceptors. Other methods disclose the type conversion as being accomplished by the selective diffusion of a dopant layer into the collector layer.