Patent ID: 11901378
Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Field: Semiconductors (Electrical engineering)
Classification: CPC H  G | IPC H

Claim 0:
1. A photodetector comprising:
a photodiode including a light absorption layer that contains germanium or a germanium compound;
a resistor connected in series with a cathode or an anode of the photodiode; and
a capacitor connected to a connection point between the resistor and the cathode or the anode, another connection point of the resistor being connected to a bias power supply, wherein
the resistor has a value between resistance values RAM and RM, both inclusive, determined by, [
  
   Math
   .
      
   1
  
  ]
 

 
  RAM
  =
  
   
    (
    
     
      E
      ⁢
      l
     
     -
     
      Pbreak
      
       M
       ⁢
          
       Pphoto_AM
      
     
    
    )
   
   ⁢
   
    (
    
     1
     
      M
      ⁢
         
      Pphoto_AM
     
    
    )
   
  
 

 
  [
  
   Math
   .
      
   2
  
  ]
 

 
  RM
  =
  
   
    (
    
     El
     -
     V_M
    
    )
   
   ⁢
   
    (
    
     1
     
      M
      ⁢
         
      Photo_M
     
    
    )
   
  
 

where R is a resistance value of the resistor, E is an electric field applied to a depletion layer of the photodiode, l is a depletion layer thickness of the photodiode, Pbreak is breakdown power of the photodiode, M is sensitivity of the photodiode, PphotoAM is maximum rated optical input power to the photodiode, PphotoM is maximum operating optical input power to the photodiode, and V_M is a value of voltage applied to the photodiode when maximum operating optical input power is input to the photodiode, and
the electric field E×the depletion layer thickness l has a value between 7 V and 12 V.