A selective epitaxial SiGe/Si planar photodetector for Si-based OEIC's

A P-i-N SiGe/Si superlattice photodetector with a planar structure has been developed for Si-based opto-electronic integrated circuits. To make the planar structure, a novel SiGe/Si selective epitaxial growth technology which uses cold wall ultrahigh-vacuum/chemical vapor deposition has been newly developed. The P-i-N planar SiGe/Si photodetector has an undoped 30-/spl Aring/ Si/sub 0.9/Ge/sub 0.1//320-/spl Aring/ Si, 30 periods, superlattice absorption layer, a 0.1-/spl mu/m P-Si buffer layer, and a 0.2-/spl mu/m P/sup +/-Si contact layer on a bonded silicon-on-insulator (/spl eta//sub ext/). The bonded SOI is used to increase the external quantum efficiency (/spl eta//sub ext/) of the photodetector. Moreover, a 63-/spl mu/m deep/128-/spl mu/m wide trench, to achieve simple and stable coupling of an optical fiber to the photodetector, is formed in the silicon chip. The P-i-N planar photodetector exhibits a high /spl eta//sub ext/ of 25-29% with a low dark current of 0.5 pA//spl mu/m/sup 2/ and a high-frequency photo response of 10.5 GHz at /spl lambda/=0.98 /spl mu/m.