High responsivity graphene photodetectors from visible to near-infrared by photogating effect

Fang Luo,Wei Luo,Yuan tan,Zhihong Zhu,Xue-Ao Zhang,Gang Peng,Honghui Sun,Mengjian Zhu,Shiqiao Qin

doi:10.1063/1.5054760

Abstract

Graphene photodetectors are highly attractive owing to its ultra-fast and wide-range spectral response from visible to infrared benefit from the superior carrier mobility and the linear dispersion with zero bandgap of graphene. The application of graphene photodetectors however is seriously limited by the low intrinsic responsivity in the order of ∼10 mA/W. Here, we demonstrate photogating field-effect transistors based on pure monolayer graphene with simple device structures. The light absorption in the heavily n-doped silicon/silicon oxide (Si/SiO2) substrate generates an additional photovoltage that effectively modulates the conductance of graphene, leading to room temperature graphene photodetectors with high responsivity of ∼500 A/W for 450 nm light and ∼4 A/W for 1064 nm light, respectively. The generated photocurrent changes with applied gate voltage and shows a strongly nonlinear power dependence. Meanwhile, the photoresponse of graphene exhibits a cut-off wavelength of ∼1100 nm, confirming the dominance photogating effect caused by light absorption in Si/SiO2 substrate. Considering the great compatibility of graphene to Si technology, our result paves a way for high-performance chip-integrated photodetectors.

Highlights

Graphene is a gapless semiconductor, allowing light absorption over a very wide wavelength spectrum ranging from ultra-violet to terahertz
Marcus et al observed that the visible light absorption in the heavily p-doped Si substrate generates a photovoltage to gate the carbon-nanotube transistors and results in a significant enhancement of photocurrent.[29]
Holes at the Si/SiO2 interface acts as an additional gate voltage, resulting in a horizontal shift in the transfer curve and generating a significant photocurrent in graphene

Summary

INTRODUCTION

Marcus et al observed that the visible light absorption in the heavily p-doped Si substrate generates a photovoltage to gate the carbon-nanotube transistors and results in a significant enhancement of photocurrent.[29] Similar mechanisms have been applied to graphene photodetectors but using lightly p-doped Si substrates.[30,31] Such photogating effect allows graphene photodetectors with both high responsivity and high bandwidth. Experimental investigations of responsivity enhanced by the photogating effect still need more efforts to gain deeper understanding of the microscopic mechanisms of graphene photodetectors. We investigate the photogating effect in graphene photodetectors by utilizing heavily n-doped Si/SiO2 as substrate. The photocurrent shows a cut-off wavelength of ∼1100 nm, indicating that the photogating effect is raised from the Si/SiO2 substrates

EXPERIMENTAL

RESULTS AND DISCUSSION

CONCLUSION