Patent ID: 7928473

Claim:
A photo-detector, comprising: a heterostructure comprising a first heterojunction comprising an n-type photon absorbing layer having an energy bandgap and a p-type middle barrier layer having an energy bandgap, said first heterojunction having an n-type δ-doping layer formed at the edge of the photon absorbing layer such that a p-n junction is formed between said barrier layer and said n-type δ-doping layer; and a second heterojunction comprising the p-type middle barrier layer and a p-type contact layer, the energy bandgap of the n-type photon absorbing layer being narrower than the energy bandgap of the middle barrier layer, the first and second heterojunctions being configured to prevent creation of a depletion region in the n-type photon absorbing layer when a bias voltage is applied across the heterostructure, wherein a tunnel current of electrons from the contact layer to the n-type photon absorbing layer is less than a dark current in the photo-detector, wherein the dark current from the photon absorbing layer to the barrier layer is essentially diffusion limited, and wherein generation recombination (GR) noise is reduced.