Photodetector and method of manufacture

Abstract

The present invention teaches a structure of a photodetector and the method of making thereof. A photodetector in accordance of the present invention is easy to fabricate, can be fabricated through low temperature processes, has high responsivity, high switching speed and high active area to device area ratio, is able to operate under photovoltaic mode or reverse bias conditions.

1 . A photodetector comprising:
 a transparent conductive oxide (TCO) layer for receiving incident photons;   a semiconductor substrate for capturing and detecting the received photons;   the TCO layer combined with the semiconductor substrate at a junction interface to form a heterojunction, wherein a TCO layer thickness is selected to minimize reflection of one or more predetermined wavelengths of the incident photons; and   a passivation layer located at the junction interface between the TCO layer and the semiconductor substrate.   
     
     
         2 . The photodetector of  claim 1 , wherein the passivation layer is less than 10 nm thick. 
     
     
         3 . The photodetector of  claim 2 , wherein the passivation layer is between 1 nm and 2 nm thick. 
     
     
         4 . The photodetector of  claim 1 , wherein the passivation layer comprises silicon oxide. 
     
     
         5 . The photodetector of  claim 1 , further comprising an optical layer located adjacent to the TCO layer, an optical layer thickness and optical layer index of refraction of the optical layer selected to maximize transmission and/or minimize absorption of a pre-defined range of wavelengths of incident photons when the optical layer is combined with the TCO layer. 
     
     
         6 . The photodetector of  claim 5 , wherein the at least one other optical layer comprises at least one other TCO layer. 
     
     
         7 . A photodetector comprising:
 a transparent conductive oxide (TCO) layer for receiving incident photons; and,   a semiconductor substrate for capturing and detecting the received photons;   the TCO layer combined with the semiconductor substrate at a junction interface to form a heterojunction; and,   a passivation layer located at the junction interface between the TCO layer and the semiconductor substrate.   
     
     
         8 . The photodetector of  claim 7 , wherein the passivation layer is less than 10 nm thick. 
     
     
         9 . The photodetector of  claim 7 , wherein the passivation layer is between 1 nm and 2 nm thick. 
     
     
         10 . The photodetector of  claim 7 , wherein the passivation layer comprises silicon oxide. 
     
     
         11 . The photodetector of  claim 7 , further comprising a TCO layer thickness selected to minimize reflection of one or more predetermined wavelengths of the incident photons. 
     
     
         12 . The photodetector of  claim 7  further comprising a voltage bias applied across the heterojunction. 
     
     
         13 . The photodetector of  claim 12 , wherein the voltage bias comprises a reverse bias. 
     
     
         14 . The photodetector of  claim 7 , wherein the semiconductor substrate is lightly doped n-type. 
     
     
         15 . The photodetector of  claim 7 , further comprising a depletion region in the semiconductor substrate adjacent to the junction interface. 
     
     
         16 . The photodetector of  claim 15 , wherein the depletion region further comprises an inversion region. 
     
     
         17 . The photodetector of  claim 7 , further comprising a back surface field region of the semiconductor substrate opposite from the junction interface, wherein the back surface field region is more heavily doped, with a same dopant type, than a rest of the semiconductor substrate. 
     
     
         18 . The photodetector of  claim 7 , further comprising a semiconductor contact covering a back surface of the semiconductor substrate, opposed from the junction interface. 
     
     
         19 . The photodetector interface of  claim 18 , wherein the semiconductor contact comprises a reflective material for reflecting the received photons back into the semiconductor substrate. 
     
     
         20 . The photodetector of  claim 7 , wherein at least one of:
 a photo-receptive surface of the TCO layer,   a back surface of the semiconductor substrate opposed from the junction interface, and a semiconductor substrate surface at the junction interface, have been treated to improve at least one optical property of that surface.   
     
     
         21 . The photodetector of  claim 7 , further comprising an optical layer located adjacent to the TCO layer, an optical layer thickness and optical layer index of refraction of the optical layer selected to maximize transmission and/or minimize absorption of a pre-defined range of wavelengths of incident photons when the optical layer is combined with the TCO layer. 
     
     
         22 . The photodetector of  claim 21 , wherein the at least one other optical layer comprises at least one other TCO layer. 
     
     
         23 . A method of manufacturing a photodetector, comprising:
 providing a semiconductor substrate; and   forming a transparent conducting oxide (TCO) layer on the semiconductor substrate, a thickness of the TCO layer selected to minimize reflection of one or more pre-determined wavelengths of incident photons.   
     
     
         24 . The method of  claim 23 , further comprising forming a passivation layer on the semiconductor substrate before forming the TCO layer. 
     
     
         25 . The method of  claim 24 , wherein the passivation layer is formed to a predetermined thickness on the semiconductor substrate. 
     
     
         26 . The method of  claim 23 , wherein the passivation layer is formed to a pre-determined composition on the semiconductor substrate. 
     
     
         27 . The method of manufacture of  claim 23 , wherein the method is performed below 300° C. 
     
     
         28 . The method of manufacture according to  claim 23 , further comprising forming a semiconductor contact on a back surface of the semiconductor substrate, opposed to the TCO layer. 
     
     
         29 . The method of manufacture according to  claim 28 , wherein the semiconductor contact comprises a reflective metal. 
     
     
         30 . The method of manufacture according to  claim 23 , further comprising forming a TCO contact on a portion of the TCO layer. 
     
     
         31 . The method of manufacture according to  claim 23 , further comprising connecting a voltage bias means to the TCO layer and the semiconductor substrate, wherein the voltage bias means is operative to apply at least one of a forward bias and a reverse bias across the TCO layer and the semiconductor substrate. 
     
     
         32 . The method of manufacture according to  claim 23 , wherein before the TCO layer is formed, the method further comprises doping a back surface field region of the semiconductor region with a higher doping concentration, with a same dopant type, than a rest of the semiconductor substrate. 
     
     
         33 . The method of manufacture according to  claim 23 , wherein the semiconductor is lightly doped n-type. 
     
     
         34 . The method of manufacture according to  claim 23 , further comprising forming at least one other optical layer located adjacent to the TCO layer, an optical layer thickness and optical layer index of refraction of the optical layer selected to maximize transmission and/or minimize absorption of a pre-defined range of wavelengths of incident photons when the optical layer is combined with the TCO layer. 
     
     
         35 . The method of manufacture according to  claim 34 , wherein the at least one other optical layer comprises at least one other TCO layer. 
     
     
         36 . The method of manufacture according to  claim 23 , further comprising:
 treating at least one of:   a photo-receptive surface of the TCO layer, a back surface of the semiconductor substrate opposed from the junction interface; and   a semiconductor substrate surface at the junction interface,   to improve at least one optical property of that surface.   
     
     
         37 . A method of manufacturing a photodetector, comprising:
 providing a semiconductor substrate; and   forming a passivation layer on the semiconductor substrate; and, forming a transparent conducting oxide (TCO) layer on the passivation layer.   
     
     
         38 . The method of  claim 37 , wherein the passivation layer is formed to a predetermined thickness on the semiconductor substrate. 
     
     
         39 . The method of  claim 37 , wherein the passivation layer is formed to a pre-determined composition on the semiconductor substrate. 
     
     
         40 . The method of  claim 37 , wherein forming the TCO layer further comprises forming the TCO layer to a thickness selected to minimize reflection of one or more pre-determined wavelengths of incident photons. 
     
     
         41 . The method of manufacture of  claim 37 , wherein the method is performed below 300° C. 
     
     
         42 . The method of manufacture according to  claim 37 , further comprising forming a semiconductor contact on a back surface of the semiconductor substrate, opposed to the TCO layer. 
     
     
         43 . The method of manufacture according to  claim 42 , wherein the semiconductor contact comprises a reflective metal. 
     
     
         44 . The method of manufacture according to  claim 37 , further comprising forming a TCO contact on a portion of the TCO layer. 
     
     
         45 . The method of manufacture according to  claim 37 , further comprising connecting a voltage bias means to the TCO layer and the semiconductor substrate, wherein the voltage bias means is operative to apply at least one of a forward bias and a reverse bias across the TCO layer and the semiconductor substrate. 
     
     
         46 . The method of manufacture according to  claim 37 , wherein before the TCO layer is formed, the method further comprises doping a back surface field region of the semiconductor region with a higher doping concentration, with a same dopant type, than a rest of the semiconductor substrate. 
     
     
         47 . The method of manufacture according to  claim 37 , wherein the semiconductor is lightly doped n-type. 
     
     
         48 . The method of manufacture according to  claim 37 , further comprising forming at least one optical layer adjacent to the TCO layer, an optical layer thickness and optical layer index of refraction selected to maximize transmission and/or minimize absorption of a predefined range of wavelengths of incident photons when the at least one optical layer is combined with the TCO layer. 
     
     
         49 . The method of manufacture according to  claim 48 , wherein the at least one other optical layer comprises at least one other TCO layer. 
     
     
         50 . The method of manufacture according to  claim 37 , further comprising:
 treating at least one of:   a photo-receptive surface of the TCO layer, a back surface of the semiconductor substrate opposed from the junction interface; and   a semiconductor substrate surface at the junction interface,   to improve at least one optical property of that surface.