Local On-Off Control of a Graphene p-n Photodetector

Abstract

Charge carriers in graphene can be n or p type, depending on chemical doping or electrostatic gating. Graphene's linear dispersion inhibits backscattering, resulting in extraordinarily high mobility (> 15000 cm2/Vs on SiO2 substrates and 200,000 cm2/Vs for suspended films), making it a promising material for high-speed electronics. Graphene is also a promising photonic material whose gapless band structure allows electron-hole pairs to be generated over a broad range of wavelengths, from UV, visible, and telecommunication bands, to IR and THz frequencies. Here, we demonstrate photoresponse in electrostatically gated graphene that appears only when and where a p-n junction is formed, allowing on-off control of photodetection. Photocurrents generated near p-n junctions do not require biasing and can be realized using submicron gates. Top-down fabrication allows integration of graphene optoelectronics into existing platforms, and can take advantage of large-area film growth.