p-SrCu₂O₂/n-ZnOヘテロ接合LEDの作製と近紫外発光

抄録

Near-UV emitting diodes composed of wide band gap oxide semiconductors, p-SrCu₂O₂ and n-ZnO heterojunctions, were fabricated and their emission properties were investigated. Single crystal ITO thin films with very flat surfaces were grown using PLD on YSZ substrates, and ZnO films were heteroepitaxially grown on the ITO surfaces. p-SrCu₂O₂(112) was preferentially grown on ZnO(0001) at 350^oC, while the preferential plane was changed into the (100) when the temperature was increased to 600^oC. This device exhibited rectifying I-V characteristics inherent to p-n junction whose turn-on voltage was about 3 V. A relatively sharp electro-luminescence band centered at 382 nm was generated by applying the forward bias voltage larger than the turn-on voltage of 3 V. The red shift in the EL peak was noticed from that of photo-luminescence (377 nm), 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. UV-LED performance characteristics such as threshold current and conversion efficiency was improved with higher SrCu₂O₂ deposition temperatures.