Thin Film Germanium-on-Insulator Photodetector and Performance Enhancement

Smart-Cut is a recently established, advanced technology for fabricating high-quality Germaniun-on-insulator (GOI) systems and has successfully applied to many devices. In this thesis, the thin film germanium layer is transferred successfully to another silicon wafer capped with about 50 nm thermal SiO2 by direct wafer bonding and hydrogen-induced layer transfer and formed the germanium-on-insulator (GOI) structure. The germanium-on-insulator can increase the responsivity and the speed of the MOS photodetector due to the large absorption in the infrared and high mobility of Ge, respectively.
In this thesis, we choose the corning 7059 glass displacing Si to be the substrate for the fabrication of GOG photodetector in order to decrease the cost and be used for back incident application. The photogenerated electron-hole pairs may recombine via defects at the Ge/SiO2 interface and consequently etching the surface of germanium layer could decrease the dark current and increase the responsivity under the visible light exposure. In addition, the ohmic contact is exchanged from aluminum to indium-tin-oxide (ITO) to apply on the GOG substrate for back incident application. This germanium-on-ITO glass structure could be used for solar cell technology. Moreover, The smart-cut technology is also applied to germanium thin film transfer to flexible polyimide and integrating with existing microelectronic equipments and process technology of semiconductor factories
Finally, the chemical bonds ‘‘Ge–CN bonds’’ are formed by a simple room temperature chemical method ‘‘crown-ether cyanide treatment’’ and they could authentically eliminate interface states at Ge/SiO2 interfaces.