| 摘要 |
PURPOSE:To obtain an avalanche multiplication type semiconductor photodetector of low noise by forming a structure that one conductive type region for forming a P-N junction is interposed between a high electric field region formed of high carrier density layer and a low electric field region of low carrier density layer. CONSTITUTION:An N type layer 1 is interposed between N<-> type layers 2, 3 having low carrier density, and a P type region 4 and a P-N junction are formed with the surface perpendicular to the laminated layer boundary of 3-layer structure as a junction surface. The carrier density of the region 4 is 10<17>-10<18>/cm<3>, the N type layer 1 has 10<16>-10<17>/cm<3>, and the layers 2, 3 has 10<16> or less. Electrons of photoexcited carries are enclosed in the layer 1 of the region having strong electric field to cause avalanche multiplication, while generated holes are removed to the layers 2, 3 of the region having weak electric field for producing no avalanche multiplication, thereby remarkably increasing the ionization ratio alpha/beta of the electrons to the holes for only the electrons to contribute to the avalanche multiplication phenomenon. |
