Graphene-Silicon-On-Insulator (GSOI) Schottky Diode Photodetectors

Abstract

Graphene-silicon (GS) Schottky junctions have been demonstrated as an efficient architecture for photodetection. However, the response speed of such devices for free space light detection has so far been limited to 10's-100's of kHz for wavelength $\lambda >$ 500nm. Here, we demonstrate graphene-silicon Schottky junction photodetectors fabricated on a silicon-on-insulator substrate (SOI) with response speeds approaching 1GHz, attributed to the reduction of the photo-active silicon layer thickness to 10$\mu$m and with it a suppression of speed-limiting diffusion currents. Graphene-silicon-on-insulator photodetectors (GSOI-PDs) exhibit a negligible influence of wavelength on response speed and only a modest compromise in responsivities compared to GS junctions fabricated on bulk silicon. Noise-equivalent-power (NEP) and specific detectivity (D$^*$) of GSOI photodetectors are 14.5pW and 7.83$\times10^{\rm{10}}$ cm Hz$^{\rm{1/2}}$W$^{\rm{-1}}$, respectively, in ambient conditions. We further demonstrate that combining GSOI-PDs with micro-optical elements formed by modifying the surface topography enables engineering of the spectral and angular response.