Single GaAs Nanowire/Graphene Hybrid Devices Fabricated by a Position-Controlled Microtransfer and an Imprinting Technique for an Embedded Structure

We developed a new technique to fabricate single nanowire devices with reliable graphene/nanowire contacts using a position-controlled microtransfer 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 nonembedded 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 noncontacted facets of the hexagonal nanowires are taken into consideration. Consistently, the nonembedded 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.