Single GaAs Nanowire/Graphene Hybrid Devices Fabricated by a Position Controlled Micro-Transfer and Imprinting Technique for Embedded Structure.

We developed a new technique to fabricate single nanowire devices with reliable graphene/nanowire contacts by using a position controlled micro-transfer and an embedded nanowire structure in a planar junction configuration. A thorough study of electrical properties and fabrication challenges of single p-GaAs nanowire/graphene devices was carried out in two different device configurations: 1) a graphene bottom-contact device where the nanowire-graphene contact junction is formed by transferring a nanowire on top of graphene and 2) a graphene top-contact device where the nanowire-graphene contact junction is formed by transferring graphene on top of an embedded nanowire. For the graphene top-contact devices, graphene-nanowire-metal devices where graphene is used as one electrode and metal is the other electrode to a nanowire, and graphene-nanowire-graphene devices where both electrodes to a nanowire are graphene were investigated and compared with conventional metal/p-GaAs nanowire devices. Conventional metal/p-GaAs nanowire contact devices were further investigated in embedded and non-embedded nanowire device configurations. A significantly improved current in the embedded device configuration is explained with a 'parallel resistors model' where the high resistance parts with the metal-semiconductor Schottky contact and the low resistance parts with non-contacted facets of the hexagonal nanowires are taken into consideration. Consistently, the non-embedded nanowire structure is found to be depleted much easier than the embedded nanowires from which an estimation for a fully depleted condition has also been established.