Photocurrent generation in lateral graphene p-n junction created by electron-beam irradiation.

Xuechao Yu,Tao Wu,Tao Liu,Qi Jie Wang,Youde Shen

doi:10.1038/srep12014

Abstract

Graphene has been considered as an attractive material for optoelectronic applications such as photodetectors owing to its extraordinary properties, e.g. broadband absorption and ultrahigh mobility. However, challenges still remain in fundamental and practical aspects of the conventional graphene photodetectors which normally rely on the photoconductive mode of operation which has the drawback of e.g. high dark current. Here, we demonstrated the photovoltaic mode operation in graphene p-n junctions fabricated by a simple but effective electron irradiation method that induces n-type doping in intrinsic p-type graphene. The physical mechanism of the junction formation is owing to the substrate gating effect caused by electron irradiation. Photoresponse was obtained for this type of photodetector because the photoexcited electron-hole pairs can be separated in the graphene p-n junction by the built-in potential. The fabricated graphene p-n junction photodetectors exhibit a high detectivity up to ~3 × 1010 Jones (cm Hz1/2 W−1) at room temperature, which is on a par with that of the traditional III–V photodetectors. The demonstrated novel and simple scheme for obtaining graphene p-n junctions can be used for other optoelectronic devices such as solar cells and be applied to other two dimensional materials based devices.

Highlights

Obtain p-n junctions in graphene devices, which imposes limitations on the device architectures and functionalities
Graphene p-n junctions with an intrinsic potential offset obtained by modulation-doped growth of large-area graphene through the chemical vapor deposition (CVD) process were reported and considerable photocurrents originated from thermoelectric effect were measured in these devices under global illuminations[19]
Single layer graphene samples were fabricated by mechanical exfoliation of highly ordered pyrolytic graphite (HOPG) on SiO2/Si wafer and verified by Raman spectroscopy

Summary

Introduction

Obtain p-n junctions in graphene devices, which imposes limitations on the device architectures and functionalities. Graphene p-n junctions with an intrinsic potential offset obtained by modulation-doped growth of large-area graphene through the chemical vapor deposition (CVD) process were reported and considerable photocurrents originated from thermoelectric effect were measured in these devices under global illuminations[19]. The physical mechanism behind it is due to the interaction of the electron beam with the Si/SiO2 interface in the substrate which induces a gating effect on the irradiated graphene. Using this novel but simple strategy, we obtained graphene photodetectors in a field effect transistor (FET) structure with high detectivity and fast response time which were found to be strongly dependent on the electron irradiation. The methodology demonstrated here enables us to modify the transport properties of graphene by electron irradiation, paving the way to fabricating graphene homo-junctions controllably and benefiting the future electronic and photonic applications of graphene and other two dimensional (2D) materials based electronic and optoelectronic devices

Methods

Results

Conclusion