Self-aligned implanted waveguide detector

Abstract

A method of fabricating a detector, the method including forming an island of detector core material on a substrate, the island having a horizontally oriented top end, a vertically oriented first sidewall, and a vertically oriented second sidewall that is opposite said first sidewall; implanting a first dopant into the first sidewall to form a first conductive region that has a top end that is part of the top end of the island; implanting a second dopant into the second sidewall to form a second conductive region that has a top end that is part of the top end of the island; fabricating a first electrical connection to the top end of the first conductive region; and fabricating a second electrical connection to the top end of the second conductive region.

1 . A method of fabricating a detector, said method comprising: 
 forming an island of detector core material on a substrate, said island having a horizontally oriented top end, a vertically oriented first sidewall, and a vertically oriented second sidewall that is opposite said first sidewall;    implanting a first dopant into the first sidewall to form a first conductive region that has a top end that is part of the top end of said island;    implanting a second dopant into the second sidewall to form a second conductive region that has a top end that is part of the top end of said island;    fabricating a first electrical connection to the top end of the first conductive region; and    fabricating a second electrical connection to the top end of the second conductive region.    
     
     
         2 . The method of  claim 1  wherein forming said island comprises: 
 forming a layer of the detector core material on the substrate; and    etching away selective portions of the detector core material layer to form said island of detector core material.    
     
     
         3 . The method of  claim 2  wherein forming said island further comprises after forming said layer of the detector core material on the substrate, forming a hard mask layer over the top end of the detector core material layer, and etching away comprises etching away selective portions of the hard mask layer and the detector core material layer to form said island of detector core material.  
     
     
         4 . The method of  claim 3  further comprising: 
 after implanting the first and second dopants, removing the hard mask layer from the top end of the island;    depositing an isolation material onto the substrate and covering said island; and    planarizing the deposited isolation material so that the top ends of the first and second conductive regions are exposed.    
     
     
         5 . The method of  claim 4  further comprising: 
 depositing an insulator onto the planarized material;    forming a first opening in the insulator above and extending down to the first conductive regions and a second opening in the insulator above and extending down to the second conductive regions; and    depositing a metal in the first and second openings to make electrical contact to the first conductive regions.    
     
     
         6 . The method of  claim 1  wherein implanting the first dopant comprises implanting a p-type dopant.  
     
     
         7 . The method of  claim 6  wherein implanting the second dopant comprises implanting an n-type dopant.  
     
     
         8 . The method of  claim 1  wherein the first and second dopants are the same.  
     
     
         9 . The method of  claim 1  wherein the first and second dopants are different.  
     
     
         10 . An optical detector comprising: 
 a substrate;    an island of detector material formed on the substrate, said island having a horizontally oriented top end, a vertically oriented first sidewall, and vertically oriented second sidewall that is opposite said first sidewall, said island having a first doped region extending into the island through first sidewall and forming a first conductive region that extends down into the island of detector material, said island also having a second doped region extending into the island through the second sidewall and forming a second conductive region that extends down into island of the detector material, the first and second conductive regions each having a top end that is part of the top end of the island;    a first electrical connection to the top end of the first conductive region; and    a second electrical connection to the top end of the second conductive region.    
     
     
         11 . The optical detector of  claim 10  further comprising: 
 an isolation material covering the first sidewall and the second sidewall of the island and forming a upper surface that is level with the top end of the island;    an insulating layer over the isolation material and the island, said insulating layer including a first hole down to the first conductive region and a second hole down to the second conductive region;    a first conductor filing the first hole and electrically connecting to the first conductive region; and    a second conductor filing the second hole and electrically connecting to the second conductive region.    
     
     
         12 . The optical detector of  claim 10  wherein the first conductive region is doped with a p-type dopant.  
     
     
         13 . The optical detector of  claim 12  wherein the second conductive region is doped with an n-type dopant.  
     
     
         14 . The optical detector of  claim 10  wherein the first and second conductive regions are doped with the same dopant.  
     
     
         15 . The optical detector of  claim 10  wherein the first and second conductive regions are doped with different dopants.