Patent ID: 8004012
Filing Date: 2011-08-23
Classification: H01L

Abstract:
1. A photo-detector comprising a semiconductor heterostructure comprising a first heterojunction, formed by a first n-type layer of a certain energy bandgap and a doped middle barrier layer, and a second heterojunction, formed by said middle barrier layer and, a second n-type layer, the layer materials being selected such that the energy bandgaps of the first and second n-type layers are narrower than that of said middle barrier layer, wherein when biased with an externally applied voltage, the more negatively biased narrow bandgap layer is a contact layer and the more positively biased narrow bandgap layer is a photon absorbing layer, the first and second heterojunctions being thus configured and operable to prevent creation of a depletion region in said photon absorbing layer when a bias voltage is applied across the heterostructure such that a tunnel current of electrons from the contact layer to the photon absorbing layer is less than a dark current in the photo-detector and the dark current from the photon-absorbing layer to said middle barrier layer is essentially diffusion limited, thus reducing generation recombination (GR) noise of the photo-detector.