nBn Infrared Detector Containing Graded Absorption Layer

It has been proposed to modify the basic structure of an nBn infrared photodetector so that a plain electron-donor-type (n-type) semiconductor contact layer would be replaced by a graded n-type III–V alloy semiconductor layer (i.e., ternary or quarternary) with appropriate doping gradient. The abbreviation “nBn” refers to one aspect of the unmodified basic device structure: There is an electron-barrier (“B”) layer between two n-type (“n”) layers, as shown in the upper part of the figure. One of the n-type layers is the aforementioned photon-absorption layer; the other n-type layer, denoted the contact layer, collects the photocurrent.