NOVELTY - A nanowire field effect junction diode comprises electrically insulating transparent substrate (130); nanowire (120) disposed on the substrate; anode (140) contacting first end of the nanowire; cathode (150) contacting second end of the nanowire; oxide layer (110) covering the nanowire; first conducting gate disposed on top of the oxide layer or adjacent with non-zero separation to the anode; and second conducting gate disposed on top of the oxide layer, adjacent with non-zero separation to the cathode or adjacent with non-zero separation the first conducting gate.    USE - A nanowire field effect junction diode for photovoltaic devices including photovoltaic sensors, switches and solar cells.    ADVANTAGE - The junction diodes can generate tunable open circuit voltage and alternating current voltage output under constant incident sunlight. A large output voltage can be obtained by properly connecting the junctions in series. The diode has large surface-volume ratios and low-cost self-assembly.    DETAILED DESCRIPTION - A nanowire field effect junction diode comprises an electrically insulating transparent substrate (130); a nanowire (120) disposed on the transparent substrate; an anode (140) contacting a first end of the nanowire; a cathode (150) contacting a second end of the nanowire; an oxide layer (110) covering the nanowire; a first conducting gate disposed on top of the oxide layer or adjacent with a non-zero separation to the anode; and a second conducting gate disposed on top of the oxide layer, adjacent with a non-zero separation to the cathode or adjacent with a non-zero separation the first conducting gate. The nanowire field effect junction diode allows activating electromagnetic radiation to pass through the electrically insulating transparent substrate. The activating electromagnetic radiation is X-ray, UV radiation, or infrared radiation. Part of the nanowire includes silicon, silicon carbide, indium phosphide, gallium nitride, or gallium arsenide.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of a silicon nanowire field effect junction diode.    Oxide layer (110)    Nanowire (120)    Electrically insulating transparent substrate (130)    Anode (140)    Cathode (150)