Fabrication and current injection UV-light emission from a transparent p-n heterojunction composed of p-SrCu2O2 and n-ZnO

UV light-emitting diode is realized for the first time using a hetero p-n junction composed of transparent conductive oxides, p-SrCu2O2 and n-ZnO. Ni/SrCu2O2/ZnO/ITO multi-layered film was epitaxially grown on an extremely flat YSZ (111) surface by a pulsed-laser deposition technique. The grown films were processed by a conventional photolithography, followed by reactive ion etching to fabricate p-n heterojunction diode. The resultant device exhibited rectifying I-V characteristics inherent to p-n junction whose turn-on voltage was about 3V relatively sharp electro-luminescence band centered at 382nm was generated when applying the forward bias voltage larger than the turn-on voltage of 3V. The red shift in the EL peak was noticed from that of photo-luminescence (377nm), which was most likely due to the difference in the excited state density between the emission processes. The EL band is attributed to transition in ZnO, probably to that associated with electron-hole plasma. The photo-voltage was also generated when the p-n junction was irradiated with UV light of which energy coincided with both exciton and band-to-band transitions in ZnO.