Integrating GeSn photodiode on a 200 mm Ge-on-insulator photonics platform with Ge CMOS devices for advanced OEIC operating at 2 µm band.

ABSTRACT

High-performance GeSn multiple-quantum-well (MQW) photodiode is demonstrated on a 200 mm Ge-on-insulator (GeOI) photonics platform for the first time. Both GeSn MQW active layer stack and Ge layer (top Ge layer of GeOI after bonding) were grown using a single epitaxy step on a standard (001)-oriented Si substrate (donor wafer) using a reduced pressure chemical vapor deposition (RPCVD). Direct wafer bonding and layer transfer technique were then employed to transfer the GeSn MQW device layers and Ge layer to a 200 mm SiO2-terminated Si handle substrate. The surface illuminated GeSn MQW photodiode realized on this platform exhibits an ultra-low leakage current density of 25 mA/cm2 at room temperature and an enhanced photo sensitivity at 2 µm of 30 mA/W as compared to a GeSn MQW photodiode on Si at 2 µm. The underlying GeOI platform enables monolithic integration of a complete suite of photonics devices operating at 2 µm band, including GeOI strip waveguides, grating couplers, micro-ring modulators, Mach-Zehnder interferometer modulators, etc. In addition, Ge CMOS circuits can also be realized on this common platform using a "photonic-first and electronic-last" processing approach. In this work, as prototype demonstration, both Ge p- and n-channel fin field-effect transistors (FinFETs) were realized on GeOI simultaneously with decent static electrical characteristics. Subthreshold swings of 150 and 99 mV/decade at |VD| = 0.1 V and drive currents of 91 and 10.3 µA/µm at |VG-VTH| = 1 V and |VD| = 0.75 V were achieved for p- and n-FinFETs, respectively. This works illustrates the potential of integrating GeSn (as photo detection material) on GeOI platform for Ge-based optoelectronics integrated circuits (OEICs) targeting communication applications at 2 µm band.