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

TL;DR

This paper reports the development of graphene-silicon-on-insulator photodetectors with response speeds nearing 1GHz, achieved by reducing silicon layer thickness, offering fast, wavelength-insensitive detection with promising noise and sensitivity metrics.

Contribution

The work introduces GSOI photodetectors with significantly improved speed and wavelength independence, utilizing SOI substrates and surface topography modifications for enhanced spectral and angular response.

Findings

Response speed approaching 1GHz.

Negligible wavelength influence on speed.

High detectivity and low noise-equivalent-power.

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.