Gate-Voltage Control of Waveguide-Coupled Lateral Ge-on-Si APD for 1550 nm Detection

Si-based avalanche photodetector (APD) covering a wide spectral range is a critical component of effective detection systems applied in optical communication, laser radar imaging, biomedical detection, and atmospheric and astronomical observation applications. In this work, a silicon-on-insulator (SOI)-based lateral APD is proposed, which consists of a waveguide, a grating coupler, a Si-based lateral p-i-n junction, and a germanium (Ge) film above the i-Si region. The experimental results show that the device has infrared detection ability at 1550 nm because of the waveguide coupling and the absorption of Ge film in the device. When the avalanche breakdown condition is reached (under a reversed bias voltage of 31 V), the ultrahigh responsivity of the device of 286.8 A/W at 1550 nm is observed. Particularly, the breakdown voltage of the device can be controlled by the back gate An obvious reduction of the breakdown voltage from 31 to 24 V is obtained under a negative gate voltage of −50 V. The responsivity as well as gain also can enhanced by applying the negative gate voltage when the device operates under the linear mode. Due to the unique detection properties, the suppressed power consumption controlled by the back gate voltage, as well as compatibility with the Si-based CMOS process, the demonstrated device is attractive in monolithic optical-electronic integrated circuits (MOEICs) and other advanced applications.