The single-crystal n-type and p-type ZnO nanowires (NWs) were synthesized via a chemical vapor deposition method, where phosphorus pentoxide was used as the dopant source. The electrical and photoluminescence studies reveal that phosphorus-doped ZnO NWs (ZnO:P NWs) can be changed from n-type to p-type with increasing P concentration. Furthermore, we report for the first time the formation of an intramolecular p-n homojunction in a single ZnO:P NW. The p-n junction diode has a high on/off current ratio of 2.5 x 10(3) and a low forward turn-on voltage of approximately 1.37 V. Finally, the photoresponse properties of the diode were investigated under UV (325 nm) excitation in air at room temperature. The high photocurrent/dark current ratio (3.2 x 10(4)) reveals that the diode has a potential as extreme sensitive UV photodetectors.

ZnO nanowire arrays were grown on semi-insulating intrinsic GaAs substrates, and controlled arsenic-doping process was carried out to realize the n-ZnO∕p-ZnO nanowire array/GaAs structures. The constructed ZnO nanowire homojunctions demonstrated a clear rectifying behavior and the turn-on voltage was above 4.0V. The corresponding ultraviolet electroluminescence spectra were obtained for the applied forward voltage above 30V (20mA). The distinct ultraviolet electroluminescence peak, centered at 382nm, is nonlinearly enhanced with an increase in the applied forward voltage. The origin of the strong ultraviolet electroluminescence was discussed in terms of the controlled arsenic-doping process.