Lateral ge/si avalanche photodetector

Abstract

A lateral Ge/Si APD constructed on a silicon-on-insulator wafer includes a silicon device layer having regions that are doped to provide a lateral electric field and an avalanche region. A region having a modest doping level is in contact with a germanium body. There are no metal contacts made to the germanium body. The electrical contacts to the germanium body are made by way of the doped regions in the silicon device layer.

1 - 47 . (canceled) 
     
     
         48 . An avalanche photodetector, comprising:
 a silicon device layer, comprising:
 a first electrical contact region including a p dopant, 
 a germanium contact region, 
 an avalanche region, 
 a charge region including the p dopant at a lower level of doping than the first contact region, separating the absorption region from the avalanche region, and 
 a second electrical contact region including an n dopant; 
   a germanium body adjacent to the germanium contact region;   a first electrical terminal in electrical communication with the first electrical contact region; and   a second electrical terminal in electrical communication with the second electrical contact region;   whereby electrons, generated in the germanium body, move into the germanium contact region and then to the avalanche region, while holes generated in the germanium body move to the second electrical contact region.   
     
     
         49 . The avalanche photodetector according to  claim 48 , wherein the germanium contact region includes a doping level that is lower than either the first electrical contact region or the charge region. 
     
     
         50 . The avalanche photodetector according to  claim 48  wherein the germanium contact region includes a doping level that is lower than either the first electrical contact region or the charge region by at least an order of magnitude. 
     
     
         51 . The avalanche photodetector according to  claim 48 , wherein the avalanche region includes a doping level that is lower than either the first electrical contact region or the charge region. 
     
     
         52 . The avalanche photodetector according to  claim 48 , wherein the germanium contact region includes a doping level that is lower than either the first electrical contact region or the charge region by approximately an order of magnitude. 
     
     
         53 . The avalanche photodetector according to  claim 48 , wherein the charge region has a dopant level of 1E15 to 1E17 per cubic centimeter. 
     
     
         54 . The avalanche photodetector according to  claim 48 , wherein the first electrical contact region and the second electrical contact region have dopant levels of greater than 1E18 per cubic centimeter. 
     
     
         55 . The avalanche photodetector according to  claim 48 , wherein the germanium body is in electrical contact with the germanium contact region and the charge region, wherein there are no metal contacts with the germanium body. 
     
     
         56 . The avalanche photodetector according to  claim 48 , wherein the germanium body is in electrical contact with the germanium contact region and the first electrical contact region, wherein there are no metal contacts with the germanium body. 
     
     
         57 . The avalanche photodetector according to  claim 48 , further comprising an oxide layer covering the germanium body, whereby there is no metal contact with the germanium body. 
     
     
         58 . The avalanche photodetector according to  claim 48 , wherein the germanium body is only in electrical contact with the germanium contact region, and not in mechanical contact with the first electrical contact region or the charge region. 
     
     
         59 . The avalanche photodetector according to  claim 48 , wherein the germanium body comprises only epitaxial germanium. 
     
     
         60 . The avalanche photodetector according to  claim 48 , wherein the germanium body comprises a triangular shape. 
     
     
         61 . The avalanche photodetector according to  claim 48 , further comprising a buffer layer between the germanium body and the silicon device layer comprising at least one of SiGe, amorphous Ge, and SiN. 
     
     
         62 . A method of fabricating an avalanche photodiode comprising:
 providing a semiconductor wafer including a silicon device layer;   producing a first electrical contact region in the silicon device layer by depositing a p dopant therein;   producing a charge region in the silicon device layer including the p dopant at a lower level of doping than the first contact region, producing a germanium contact region adjacent the first electrical contact region and the charge region;   producing a second electrical contact region in the silicon device layer including an n dopant, producing an avalanche region adjacent the charge region and the second electrical contact region;   depositing a germanium body in contact with the germanium contact region;   applying a first electrical terminal in electrical communication with the first electrical contact region; and   applying a second electrical terminal in electrical communication with the second electrical contact region.   
     
     
         63 . The method according to  claim 62 , wherein both the germanium contact region and the avalanche region include a doping level that is lower than either the first electrical contact region or the charge region. 
     
     
         64 . The method according to  claim 62 , wherein the charge region is doped at a dopant level of 1E15 to 1E17 per cubic centimeter. 
     
     
         65 . The method according to  claim 62 , wherein the first electrical contact region and the second electrical contact region are doped at dopant levels of greater than 1E18 per cubic centimeter. 
     
     
         66 . The method according to  claim 62 , wherein the germanium body is only in electrical contact with the germanium contact region, and not in mechanical contact with the first electrical contact region or the charge region. 
     
     
         67 . The method according to  claim 62 , wherein the germanium body is deposited with germanium epitaxy.