Application of reduced dark current photodetector with a thermoelectric cooler

Abstract

A IDCA system combining thermo-electric cooler (TEC) and an internal nBn photo-detector having a photo absorbing layer comprising an n-doped semiconductor exhibiting a valence band energy level; and a contact layer comprising a doped semiconductor. A barrier layer is disposed between the photo absorbing layer and the contact layer, the barrier layer exhibiting a valence band energy level substantially equal to the valence band energy level of the doped semiconductor of the photo absorbing layer; the barrier layer exhibiting a thickness and a conductance band gap sufficient to prevent tunneling of majority carriers from the photo absorbing layer to the contact area and block the flow of thermalized majority carriers from the photo absorbing layer to the contact area. Alternatively, a p-doped semiconductor is utilized, and conductance band energy levels of the barrier and photo absorbing layers are equalized.

What is claimed is: 
     
       1. An integrated dewar cooler system comprising:
 a light permitting optical window; 
 a sealed Dewar; 
 a thermoelectric Cooler; and 
 a focal plane array, 
 wherein said focal plane array is an array of photo detectors with a reduced dark current, comprising: 
 a photo absorbing layer comprising a doped semiconductor exhibiting a valence band energy and a conducting band energy during operation of the photo-detector; 
 a barrier layer comprising an undoped semiconductor, the barrier layer having a band energy gap and associated conduction and valence band energies, a first side of said barrier layer adjacent a first side of said photo absorbing layer; and 
 a contact layer comprising a doped semiconductor exhibiting a valence band energy and a conducting band energy during operation of the photo-detector, said contact layer being adjacent a second side of said barrier layer opposing said first side; 
 
       wherein the relationship between the photo absorbing layer and contact layer valence and conduction band energies and the barrier layer conduction and valance band energies facilitates minority carrier current flow while inhibiting majority carrier current flow between the contact and photo absorbing layers; and,
 wherein said contact layer comprises individual sections which are separate from each other in a direction across the photo-detector, each section corresponding to an individual detector element, wherein said barrier layer extends past the individual sections of the contact layer in the direction across the photo-detector, and is monolithically provided for each of the individual detector elements, thereby passivating the photo-detector during operation by blocking the flow of majority carriers to exposed surfaces of said barrier layer. 
 
     
     
       2. An integrated dewar cooler as claimed in  claim 1 , wherein the dewar is at least partially evacuated. 
     
     
       3. An integrated dewar cooler as claimed in  claim 1 , wherein the dewar is at least partially filled with an inert gas.