Reduced dark current photodetector

Abstract

A photo-detector comprising: a photo absorbing layer comprising an n-doped semiconductor exhibiting a valence band energy level; a barrier layer, a first side of the barrier layer adjacent a first side of the photo absorbing 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; and a contact area comprising a doped semiconductor, the contact area being adjacent a second side of the barrier layer opposing the first side, 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.

1 . A photo-detector comprising:
 a photo absorbing layer comprising a doped semiconductor exhibiting a valence band energy level and a conducting band energy level;   a barrier layer, a first side of said barrier layer adjacent a first side of said photo absorbing layer, said barrier layer exhibit a valence band energy level substantially equal to said valence band energy level of said photo absorbing layer and a conduction band energy level exhibiting a significant band gap in relation to the conduction band of said photo absorbing layer; and   a contact layer comprising a doped semiconductor, said contact layer being adjacent a second side of said barrier layer opposing said first side,   said barrier layer exhibiting a thickness, said thickness and said band gap being sufficient to prevent tunneling of majority carriers from said photo absorbing layer to said contact layer and blow the flow of thermalized majority carriers from said photo absorbing layer to said contact layer.   
     
     
         2 . A photo-detector according to  claim 1 , wherein said barrier layer comprises an undoped semiconductor. 
     
     
         3 . The photo-detector according to  claim 1 , wherein the photo absorbing layer and the contact layer are either both n-doped or both p-doped. 
     
     
         4 . A photo-detector according to  claim 1 , wherein said contact layer exhibits a valence band energy level substantially equal to or greater than said valence band energy level of said doped semiconductor of said photo absorbing layer. 
     
     
         5 . A photo-detector according to  claim 1 , further wherein said photo-detector has not been subjected to a passivation process. 
     
     
         6 . The photo-detector according to  claim 1 , wherein the alignments of respective edges of the valence band energy and conduction band energy at interfaces between the photo absorbing layer and the barrier layer and between the contact layer and the barrier layer occur with minimized depletion zones. 
     
     
         7 . A photo-detector according to  claim 1 , wherein said photo absorbing layer is operable to generate carriers in the presence of light energy exhibiting a wavelength of 3-5 microns. 
     
     
         8 . A photo-detector according to  claim 1 , further comprising a substrate exhibiting a first side adjacent a second side of said photo absorbing layer, said second side of said photo absorbing layer opposing said first said of said photo absorbing layer, said substrate exhibiting a second side in contact with a first metal layer. 
     
     
         9 . A photo-detector according to  claim 1 , wherein said barrier layer comprises one of AlSb, AlAsSb, GaAlAsSb, AlPSb, AlGaPSb and HgZnTc. 
     
     
         10 . A photo-detector comprising:
 a photo absorbing layer comprising an p-doped semiconductor exhibiting a conduction band energy and valence band energy;   a barrier layer exhibiting a thickness, a first side of said barrier layer adjacent a first side of said photo absorbing layer; and   a contact layer comprising a doped semiconductor, said contact layer adjacent a second side of said barrier layer opposing said first side,   wherein said barrier layer exhibits a conduction band energy substantially equal to said conduction band energy of said photo absorbing layer and a valence band energy less than the valence band energy of said photo absorbing layer such that a valence energy band gap is formed between the photo absorbing layer and the barrier layer,   wherein said barrier layer thickness and said valence energy band gap are sufficient to prevent tunneling of majority carriers from said photo absorbing layer to said contact layer and to substantially block the flow of thermalized majority carriers from said photo absorbing layers to said contact layer, and   further wherein during operation said barrier layer functions to achieve passivation of the photo-detector.   
     
     
         11 . A photo-detector according to  claim 10 , wherein said barrier layer comprises an undoped semiconductor. 
     
     
         12 . A photo-detector according to  claim 10 , wherein said contact layer is either n-doped or p-doped. 
     
     
         13 . A photo-detector according to  claim 10 , wherein said contact layer exhibits a conduction band energy equal to or less than said conduction band energy of said barrier layer, and
 wherein said conduction band energy of said barrier layer is less than said conduction band energy of said p-doped semiconductor of said photo absorbing layer.   
     
     
         14 . A photo-detector according to  claim 14 , wherein said photo absorbing layer is operable to generate minority carriers in the presence of light energy exhibiting a wavelength of 3-5 microns. 
     
     
         15 . A photo-detector according to  claim 10 , further comprising a second metal layer in contact with said contact layer. 
     
     
         16 . A photo-detector according to  claim 10 , wherein said barrier layer comprises one of AlSb, AlAsSb, GaAlAsSb, AlPSb, AlGaPSb, InAlAs, InAlAsSb, and HgZnTe. 
     
     
         17 . A photo-detector according to  claim 10 , wherein said photo absorbing layer is constituted of one of p-doped InAs, p-doped InAsSb, p-doped InGaAs, p-doped Type II super lattice InAs/InGaSb and p-doped HgCdTe. 
     
     
         18 . A method of producing a photo-detector, the method comprising:
 providing a substrate;   depositing on said substrate a photo-absorbing layer comprising a doped semiconductor exhibiting an energy level associated with non-conducting majority carriers;   depositing on said deposited photo absorbing layer a barrier layer exhibiting a thickness, an energy level associated with minority carriers of said photo absorbing layer substantially equal to said energy level of said photo absorbing layer and a band gap associated with majority carriers of said photo absorbing layer; and   depositing on said deposited photo absorbing layer a contact layer comprising a doped semiconductor,   said thickness and said band gap of said barrier layer being sufficient to prevent tunneling of majority carriers from said photo absorbing layer to said contact layer and to block the flow of thermalized majority carriers from said photo absorbing layer to said contact layer.   
     
     
         19 . A method according to  claim 18 , further comprising selectively etching said deposited contact layer to define a plurality of contact areas. 
     
     
         20 . A method according to  claim 18 , wherein at least one of depositing said photo absorbing layer, depositing said barrier layer and depositing said contact layer is done via one of molecular beam epitaxy, metal organic chemical vapor deposition, metal organic phase epitaxy and liquid phase epitaxy.