Closely-spaced VCSEL and photodetector for applications requiring their independent operation

Abstract

A monolithically integrated VCSEL and photodetector, and a method of manufacturing the same, are disclosed for applications where the VCSEL and photodetector require separate operation such as duplex serial data communications applications. A first embodiment integrates a VCSEL with an MSM photodetector on a semi-insulating substrate. A second embodiment builds layers of a p-i-n photodiode on top of layers forming a VCSEL using a standard VCSEL process. The p-i-n layers are etched away in areas where VCSELs are to be formed and left where photodetectors are to be formed. The VCSELs underlying the photodetectors are inoperable, and serve to recirculate photons which are not initially absorbed back into the photodetector. The transmit and receive pairs are packaged into a single package for interface to multifiber ferrules. The distance between the devices is precisely defined photolithographically, thereby making alignment easier. In a further alternate embodiment, a FET is coupled to the p-i-n photodiode to form an integrated detector preamplifier along with the VCSEL transmitter all on the same optical reference plane.

1 . A monolithic optical transmitter and receiver pair comprising: 
 a substrate;    an optical transmitter formed on said substrate;    an optical receiver formed laterally adjacent to said optical transmitter; and    an isolation region to electrically isolate said optical transmitter from said optical receiver.    
     
     
         2 . The monolithic optical transmitter and receiver pair of  claim 1  wherein the optical receiver comprises a photodiode.  
     
     
         3 . The monolithic optical transmitter and receiver pair of  claim 1  wherein the optical transmitter comprises a VCSEL having a plurality of layers.  
     
     
         4 . The monolithic optical transmitter and receiver pair of  claim 3 , wherein the substrate is a semiconductor wafer, and wherein the plurality of VCSEL layers comprise: 
 a first mirror formed on the semiconductor wafer;    a first cladding layer formed on said first mirror;    an active region formed on said first cladding layer;    a second cladding layer formed on said active region; and    a second mirror layer formed on said second cladding layer.    
     
     
         5 . The monolithic optical transmitter and receiver pair of  claim 3  wherein the optical receiver comprises: 
 a p-type layer formed on at least a portion of said VCSEL layers;  
 an intrinsic layer formed on said p-type layer; and  
 an n-type layer formed on said intrinsic layer.  
 
     
     
         6 . The monolithic optical transmitter and receiver pair of  claim 5 , wherein the isolation region comprises a proton implant region.  
     
     
         7 . The monolithic optical transmitter and receiver pair of  claim 3 , wherein the VCSEL layers further comprise a dielectric phase shifting layer.  
     
     
         8 . The monolithic optical transmitter and receiver pair of  claim 1 , further comprising at least one transistor coupled to the optical receiver.  
     
     
         9 . The monolithic optical transmitter and receiver pair of  claim 8 , wherein the optical transmitter comprises a VCSEL having a plurality of layers, the transistor formed over at least a portion of said VCSEL layers.  
     
     
         10 . The monolithic optical transmitter and receiver pair of  claim 9 , wherein the transistor is a field effect transistor.  
     
     
         11 . The monolithic optical transmitter and receiver pair of  claim 10 , wherein the isolation region forms a conductive well for the transistor.  
     
     
         12 . The monolithic optical transmitter and receiver pair of  claim 1 , wherein the isolation region comprises a proton implant region.  
     
     
         13 . The monolithic optical transmitter and receiver pair of  claim 1 , further comprising an anti-reflective coating formed on said optical receiver.  
     
     
         14 . A method of manufacturing a monolithic optical transmitter and receiver pair, comprising: 
 forming an optical transmitter on a semiconductor substrate;    forming an optical receiver adjacent to the optical transmitter; and    forming an isolation region between the optical transmitter and the optical receiver.    
     
     
         15 . The method of  claim 14 , wherein the step of forming an optical transmitter comprises: 
 forming a first mirror on the semiconductor substrate;    forming a first cladding layer on the first mirror;    forming an active region on the first cladding layer;    forming a second cladding layer on the active region; and    forming a second mirror layer on the second cladding layer.    
     
     
         16 . The method of  claim 15 , wherein the step of forming an optical receiver comprises: 
 forming a p-type layer on at least a portion of the optical transmitter layers;    forming an intrinsic layer on the p-type layer; and    forming an n-type layer on the intrinsic layer.    
     
     
         17 . The method of  claim 15 , further comprising forming a dielectric phase shifting layer.  
     
     
         18 . The method of  claim 14 , wherein the step of forming an isolation region comprises forming a proton implant region.  
     
     
         19 . The method of  claim 14 , further comprising: 
 forming a transistor electrically coupled to the optical receiver for amplifying signals generated by the optical receiver.    
     
     
         20 . The method of  claim 14 , wherein the optical receiver is formed on the semiconductor substrate.