Patent ID: 8178843
Filing Date: 2012-05-15
Classification: H01L

Abstract:
1. A high impedance low noise midwave infrared lead salt photodetector having enhanced photoconductive gain, comprising: a surface oxide layer; a wide-gap cap therebeneath; a surface channel beneath said wide-gap cap; a depletion region under said surface channel; and, a pair of horizontally spaced apart electrodes to either side of said depletion region to create a built-in electric field and current flow that are orthogonal to establish a horizontal surface flow, the built-in field separating carriers and enhancing lifetime, said photodetector having been formed using a molecular beam epitaxially grown heterostructure lead salt with a wide-gap surface layer that creates a surface channel for minority carriers on top of said depletion region, in which said horizontal current flows in the depletion region between said horizontally spaced-apart electrodes to produce photoconductive gain in the horizontal current flow, said surface channel reducing the speed at which the minority carriers recombine due to the exclusion of majority carriers by a built-in electric field such that room temperature lifetimes are enhanced as compared to a photodetector that includes a bulk polycrystalline material, the photo detector structure at the same time providing a high detector impedance, low noise output without sacrificing photo conductive gain.