JPS6457765A - Semiconductor photodetector - Google Patents

Abstract

PURPOSE:To reduce the noise and to accelerate the speed of an APD(Avalanche Photodiode) by employing GaInAs having specific impurity concentration or less as the absorption layer of the APD, eliminating the avalanche multiplication of carrier by this layer, and implanting only electrons to a superlattice multiplying layer. CONSTITUTION:An n-type superlattice (n-type AlInAs/GaInAs) 2 as a multiplying layer, an n-type GaInAs layer 3 as an optical absorption layer and an n-type InP layer 4 as an optical transmitting layer are sequentially grown on an n<+> type InP substrate 1, and Zn or Cd is so diffused as p-type impurity from the surface of the layer 4 as to arrive at the layer 3 to form a p<+> type region 5. When a multiplying electric field is represented by Em and n-type impurity concentration is represented by N, the Em of the optical absorption is larger than that of the superlattice multiplying layer at N=2X10<16>cm<-3> or less, and it is reversed at 2X10<16>cm<-3> or more. The superlattice multiplying layer has Em=1.5X10<5>Vcm<-1> at N=2X10<16>cm<-3>, Accordingly, when the impurity concentration of the optical absorption layer is set to 2X10<16>cm<-3> or less, its avalanche multiplication can be mainly performed only by the superlattice multiplying layer, and only electrons are implanted from the optical absorption layer to the superlattice multiplying layer.