Sige photodiode

Abstract

The lattice mismatching between a Ge layer and a Si layer is as large as about 4%. Thus, when the Ge layer is grown on the Si layer, penetration dislocation is introduced to cause leakage current at the p-i-n junction. Thereby, the photo-detection sensitivity is reduced, and the reliability of the element is also lowered. Further, in the connection with a Si waveguide, there are also problems of the reflection loss due to the difference in refractive index between Si and Ge, and of the absorption loss caused by a metal electrode. In order to solve said problems, according to the present invention, there is provided a vertical type pin-SiGe photodiode having a structure which is embedded in a groove formed in a part of a Si layer, in which a p-type or n-type doped layer is formed in a lower section of the groove, and in which a i-SiGe layer having a rectangular shape or a reverse tapered shape is formed on a layered structure formed by laminating a i-Si layer and a SiGe buffer layer on the lower section and the side wall of the groove. Further, in an optical connection section with a Si waveguide, impedance matching is effected by the layered structure composed of the i-Si layer and the SiGe buffer layer, and an upper metal layer is separated therefrom so that a poly-Si bridge structure is employed to electrically connect the upper metal layer therewith.