Abstract
Germanium (Ge) has many interesting optical and electrical properties, enabling unique optoelectronic
integrated circuits operating at near-infrared and mid-infrared wavelengths. To integrate a Ge thin membrane
on Si, we have developed direct wafer bonding and Smart-cutTM for Ge. Through the process optimization,
we have successfully obtained a high-quality Ge-on-insulator (GeOI) wafer. Using a GeOI
wafer, we have fabricated a near-infrared Ge photodetector monolithically integrated with an amorphous
Si waveguide. Since Ge is transparent at mid-infrared wavelengths from 2 μm to 14 μm, we have proposed
a Ge mid-infrared photonic integrated circuit on a GeOI wafer. We have demonstrated ultrasmall
Ge waveguide components as well as carrier-injection optical modulators and defect-mediated photodetectors.
