AVALANCHE PHOTODIODE

摘要

A practical germanium avalanche photodiode (Ge APD) for use with 1.5 mu m band light with which a silica optical fibre has a minimum transmission loss is provided by forming a reach-through type Ge APD having a P<+>NN<-> structure. Typically the photodiode includes an N<-> type substrate 1 with a P<+> type region 2 in the substrate and adjacent its surface with an N type region 3 interposed between the P<+> type region 2 and the N<-> type region 1. Preferably the P<+> type region 2 and the N type region 3 are surrounded by a P type region 4 forming a guard ring. It is further preferred that the doping concentration of the N<-> type region 1 is below 1 x 10<1><5> cm<-><3> and the doping of the N type region 3 is between 1 x 10<1><6> and 1 x 10<1><7> cm<-><3>.