Fabrication and Electronic Investigation of GaAs nanowire/Graphene Hybrid Devices

Abstract

In the present study, a process for fabricating GaAs nanowire/graphene hybrid devices using electron beam lithography processing techniques is presented and demonstrated. Fabricated devices were investigated electronically by measuring emph{I-V} characteristics under a variable gate voltage.Fabrication processes for both exfoliated and CVD-grown graphene were developed. For exfoliated graphene the outlined process is unsuccessful, as the graphene flakes were found to crumble and fall off during the first processing step following transfer. It is thus concluded that exfoliated graphene flakes are too delicate to perform any significant processing after graphene transfer.The fabrication process was successfully demonstrated in fabrication of devices with CVD-grown graphene. However, nanowires in these devices were seen to undergo significant corrosion during the process, which is credited to the water exposure associated with graphene transfer. This was found to be an especially prominent issue for contacted nanowires, where the metal contact is believed to facilitate galvanic corrosion. I-V characteristics and gate voltage dependence were measured for GaAs nanowire/graphene hybrid devices made with CVD-grown graphene. Large variations in the I-V behavior and gate voltage dependence was observed. This is credited to corrosion in the nanowires, which is thought to result in uncharacteristic behavior for metal-GaAs contacts. There are also indications that several devices are shortened by graphene. The electronic investigations are therefore found to be inconclusive in respect to the electronic properties of the graphene/GaAs nanowire junction. It is concluded that further developments in the fabrication process are needed to achieve GaAs nanowire/graphene hybrid devices suitable for detailed analysis.