Photoresponsive device and method for fabricating the same, including composition grading and recessed contacts for trapping minority carriers

摘要

A mercury-cadmium-telluride (HgCdTe) photoresponsive layer (14) having the composition Hg1-xCdxTe is formed on a substrate (12) such that x increases from the surface (14a) of the photoresponsive layer (14) toward the substrate (12). This causes the bandgap in the photoresponsive layer (14) to increase from the surface (14a) toward the substrate (12), thereby urging minority carriers which are photogenerated in the photoresponsive layer (14) to move toward and be trapped at the surface (14a). Laterally spaced first and second ohmic contacts (16,18) are electrically connected to the photoresponsive layer (14) at a predetermined distance (zc) below the surface (14a) such that the photogenerated minority carriers trapped at the surface (14a) are urged away from the contacts (16,18) by the increasing bandgap. An electrically floating photoresponsive layer (24) of opposite conductivity type may be formed between the substrate (12) and the photoresponsive layer (14) to form a Heterojunction Interface Trap.