Doped Absorption For Enhanced Responsivity For High Speed Photodiodes

Abstract

A photodiode with a semiconductor intrinsic light absorption layer has at least one p-doped light absorption layer or an n-doped light absorption layer, and preferably both. The diode also has a cathode electrode and an anode electrode electrically coupled with the p-doped light absorption layer or the n-doped light absorption layer.

1 - 18 . (canceled)  
     
     
         19 . A photodiode structure for generating an electrical current in response to light incident thereon comprising: 
 a light-absorption intrinsic semiconductor layer, having a thickness ti and a doping concentration below 3e15 cm −3 , which is operative to absorb light incident thereon and to produce, in response said incident light absorbed thereby, electrical carriers that are transported therethrough;    a first light absorption doped semiconductor layer doped with one of p- and n-conductivity type-determining impurities, and having a thickness tdl and a doping concentration dc 1  between 1e16 and 5e18 cm −3 , and having a first surface thereof abutting a first surface of said light absorption intrinsic semiconductor layer, and which is operative to absorb light incident thereon and to produce, in response to said incident light absorbed thereby, electrical carriers that are transported therethrough, and wherein td 1 /ti is greater than or equal to 0.17; and    an electrode arrangement for extracting electrical current comprised of said carriers produced by and transported through said light-absorption intrinsic semiconductor layer and said first light absorption doped semiconductor layer, said electrode arrangement including a first electrode electrically coupled to said first light absorption doped semiconductor layer, and a second electrode electrically coupled to said light absorption intrinsic semiconductor layer.    
     
     
         20 . The photodiode structure according to  claim 19 , further comprising a second light absorption doped semiconductor layer doped with the other of said p- and n-conductivity type-determining impurities, having a thickness td 2 , and a doping concentration dc 2  between 1e16 and 5e18 cm −3 , said second light absorption doped semiconductor layer having a first surface thereof abutting a second surface of said light absorption intrinsic semiconductor layer that is spaced apart from said first surface of said light absorption intrinsic semiconductor layer by material of said light absorption intrinsic semiconductor layer therebetween, said second light absorption semiconductor layer being operative to absorb light incident thereon and to produce, in response to said incident light absorbed thereby, electrical carriers that are transported therethrough, and wherein (td 1 +td 2 )/ti is greater than or equal to 0.17, and wherein 
 said electrode arrangement is operative to extract electrical current comprised of said carriers produced by and transported through said light-absorption intrinsic semiconductor layer and said first and second light absorption doped semiconductor layers, and includes said first electrode electrically coupled to said first light absorption doped semiconductor layer, and said second electrode electrically coupled to said second light absorption doped semiconductor layer.    
     
     
         21 . The photodiode structure according to  claim 20 , wherein said first light absorption doped semiconductor layer comprises a light absorption p-doped semiconductor layer and said second light absorption doped semiconductor layer comprises an n-doped semiconductor layer, and wherein 
 said electrode arrangement comprises a p-doped anode electrode electrically coupled to a second surface of said light absorption p-doped semiconductor layer, and an n-doped cathode electrode electrically coupled to a second surface of said light absorption n-doped semiconductor layer.    
     
     
         22 . The photodiode structure according to  claim 19 , wherein the total thickness tdl+ti of said first light absorption doped semiconductor layer and said light absorption intrinsic semiconductor layer is greater than v/(2f 3-dB ) by 20% or more, where v is the saturation drift velocity of either an electron or a hole, whichever is smaller, in said light absorption intrinsic semiconductor layer, and wherein f 3-dB  is the frequency at which the amplitude of responsivity of said photodiode structure is reduced to 1/√{square root over (2)} of its DC low-frequency value.  
     
     
         23 . The photodiode structure according to  claim 20 , wherein the total thickness td 1 +td 2 +ti of said first and second light absorption semiconductor layers and said light absorption intrinsic semiconductor layer is greater than v/(2f 3-dB ) by 20% or more, where v is the saturation drift velocity of either an electron or a hole, whichever is smaller, in said light absorption intrinsic semiconductor layer, and wherein f 3-dB  is the frequency at which the amplitude of responsivity of said photodiode structure is reduced to 1/√{square root over (2)} of its DC low-frequency value.  
     
     
         24 . The photodiode structure according to  claim 19 , wherein, at a 3-dB bandwidth frequency of 40 GHz or higher, said first light absorption doped semiconductor layer and said light absorption intrinsic semiconductor layer are InGaAs lattice-matched to InP, and the total thickness (tdl+ti) of said first light absorption doped semiconductor layer and said light absorption intrinsic semiconductor layer is greater than 0.60 microns.  
     
     
         25 . The photodiode structure according to  claim 19 , wherein, at a  3 -dB bandwidth frequency of  40 GHz or higher, said first light absorption doped semiconductor layer and said light absorption intrinsic semiconductor layer are InGaAs lattice-matched to InP, and the total thickness (td 1 +ti) of said first light absorption doped semiconductor layer and said light absorption intrinsic semiconductor layer is greater than  0 . 65  microns.  
     
     
         26 . The photodiode structure according to  claim 19 , wherein, at a 3-dB bandwidth frequency of 40 GHz or higher, said first light absorption doped semiconductor layer and said light absorption intrinsic semiconductor layer are InGaAs lattice-matched to InP, and the total thickness (tdl+ti) of said first light absorption doped semiconductor layer and said light absorption intrinsic semiconductor layer is greater than 0.70 microns.  
     
     
         27 . The photodiode structure according to  claim 20 , wherein, for a 3-dB bandwidth frequency of 40 GHz or higher, said first and second light absorption doped semiconductor layers and said light absorption intrinsic semiconductor layer are InGaAs lattice-matched to InP, and the total thickness (td 1 +td 2 +ti) of said first and second light absorption doped semiconductor layer and said light absorption intrinsic semiconductor layer is greater than 0.60 microns.  
     
     
         28 . The photodiode structure according to  claim 20 , wherein, for a 3-dB bandwidth frequency of 40 GHz or higher, said first and second light absorption doped semiconductor layers and said light absorption intrinsic semiconductor layer are InGaAs lattice-matched to InP, and the total thickness (td 1 +td 2 +ti) of said first and second light absorption doped semiconductor layer and said light absorption intrinsic semiconductor layer is greater than 0.65 microns.  
     
     
         29 . The photodiode structure according to  claim 20 , wherein, for a 3-dB bandwidth frequency of 40 GHz or higher, said first and second light absorption doped semiconductor layers and said light absorption intrinsic semiconductor layer are InGaAs lattice-matched to InP, and the total thickness (td 1 +td 2 +ti) of said first and second light absorption doped semiconductor layer and said light absorption intrinsic semiconductor layer is greater than 0.70 microns.