Heterogeneous integration of III-V compound semiconductors and Ge on the Si platform is one of the promising technologies for enhancing the performance of metal-oxide-semiconductor field effect transistors (MOSFETs) beyond the 10-nm technology node because of their high carrier mobilities. In addition, the III-Vs and Ge are also promising materials for photonic devices. Thus, we have investigated III-V/Ge device engineering for CMOS photonics, enabling monolithic integration of high-performance III-V/Ge CMOS transistors and III-V/Ge photonics on Si. The direct wafer bonding of III-V on Si has been investigated to form III-V on Insulator for III-V CMOS photonics. Extremely-thin-body InGaAs MOSFETs with the gate length of approximately 55 nm have successfully been demonstrated by using the wafer bonding. InP-based photonic-wire waveguide devices including micro bends, arrayed waveguide gratings, grating couplers, optical switches, and InGaAs photodetectors have also been demonstrated on the III-V-OI wafer. The gate stack formation on Ge is one of the critical issues for Ge MOSFETs. Recently, we have successfully demonstrated high-quality GeOx/Ge MOS interfaces formed by thermal oxidation and plasma oxidation. High-performance Ge pMOSFET and nMOSFET with thin EOT have been obtained using the GeOx/Ge MOS interfaces. We have also demonstrated that GeOx surface passivation is effective to reduce the dark current of Ge photodetectors in conjunction with gas-phase doped junction. We have also investigated strained SiGe optical modulators. We expect that compressive strain in SiGe enhances modulation efficiency, and an extremely small VπL of 0.033 V-cm is predicted. III-V/Ge heterogeneous integration is one of the promising ways for achieving ultrahigh performance electronic-photonic integrated circuits.
Coupling schemes for heterogeneous integration of III-V membrane devices and silicon-on-insulator waveguides
