A High-Speed Waveguide Integrated InSe Photodetector on SiN Photonics for NIR Applications

On-chip integration of two-dimensional (2D) materials offers great potential for the realization of novel optoelectronic devices in different photonic platforms. In particular, indium selenide (InSe) is a very promising 2D material due to its ultra-high carrier mobility and outstanding photo-responsivity. Here, we report a high-speed photodetector based on a multilayer 90 nm thick InSe integrated on a silicon nitride (SiN) waveguide. The device exhibits a low dark current of 10 nA at 1V bias, a remarkable photoresponsivity of 0.38 AW-1, and high external quantum efficiency of 48.4% measured at 5 V bias. This performance is tested at near-infrared (NIR) 976 nm wavelength under ambient conditions. Furthermore, using numerical and experimental investigations, the estimated absorption coefficient per unit length is 0.11dB/um. To determine the dynamic response of the photodetector, its small and large signal frequency response are also evaluated. A 3-dB radiofrequency (RF) bandwidth of 85 MHz is measured with an open-eye diagram observed at 1 Gbit/s data transmission. Given these outstanding optoelectronic merits, active photonic devices based on integrated multilayer InSe can be realized for a variety of applications including short-reach optical interconnects, LiDAR imaging, and biosensing.