| 摘要 |
PURPOSE:To form a guard ring in a step of diffusing at low temperature for a short time by selectively removing a semiconductor layer forming the surface of a semiconductor photodetector prior to the step of diffusing impurity. CONSTITUTION:An n type InP buffer layer 2, an n type InGaAs layer 3, an n type InP layer 4, and an n type InP layer 5 are sequentially formed on an n<+>-type InP substrate 1. Then, an SiO2 film mask 6 is formed on the layer 5, and the layer 5 not with the mask 6 is removed by a selective etching. After the mask 6 is separated, a diffusing mask 7 is formed, Cd is diffused in the layers 4, 5 to simultaneously form p<+> type InP regions 8, 9. The region 8 becomes a guard ring, and the region 9 becmes a photodetector. Since the formation of the guard ring can be accordingly formed in the step of diffusing at a low temperature for a short time, it can reduce the crystalline defects, thereby obtaining a stable avalanche breakdown. |
