Electrical properties of individual single-crystalline gallium phosphide nanowires with an outer oxide shell

High-quality single-crystalline GaP nanowires were grown by a simple vapour deposition method and their electrical and opto-electric transport properties were studied. Structural studies showed that the GaP nanowires consisted of a core-shell structure with a single-crystalline GaP core and an outer gallium oxide (GaO_x) layer of thickness ∼6 nm. The individual GaP nanowires exhibited n-type field effects with an on/off ratio as high as 10 ⁵ and their carrier mobilities are in the range of about 10-22 cm² V^-1 s^-1 at room temperature. When the devices were exposed to an ultraviolet (UV) light source, the current in the nanowires increased abruptly to more than 10³ times, and this was possibly due to carrier generation in the nanowires and de-adsorption of adsorbed O₂^- ions on the GaO_x surface shell. The nanowires also showed good reversible switching actions between the high- and low-resistance states.