| Zinc oxide is a II-VI wide band-gap (3.37 eV) compound semiconductor with wurtzite crystal structure and the high exciton binding energy of 60 meV. This material has attracted extensive interest in the filed of electrical and optical devices because of its multi-functionality. ZnO is presently widely used in piezoelectric transducers, varistors, gas sensors, and transparent conducting films, which is important for the photovoltaic industry. Due to the large exciton binding energy of 60meV, which ensures the high efficient excitonic emission at room temperature, it is regarded as one of the most promising materials for fabricating efficient ultraviolet (UV) and blue light emitting devices. Since the first observation of the stimulated ultraviolet emission at room temperature, ZnO has become another hotspot in the region of UV light emitting researching. ZnO has a potential to play an important role in the semiconductor field in future. High quality metal-ZnO contacts are critical for ZnO device applications. Developing improved Ohmic and rectifying contacts to both conductivity types of ZnO are the basic building blocks for any advanced device technology in ZnO.Iridium oxide (IrO2), as a well-known conductive oxide material, has attractive electrical, and chemical properties. Iridium oxide thin films have attracted attentions as an excellent bottom electrode and a good thermal barrier layer. In this paper, we fabricate IrO2/ZnO contacts by pulsed-laser deposition ( PLD). The electrical properties and thermal stability have been studied. The experimental results show that the IrO2 thin films have low electrical resistivity and are transparent at a wavelength range from 500 to 800 nm. The Ohmic contacts of IrO2/n-ZnO were relatively thermally stable at 600℃annealing temperature in N2. The transition to rectifying characteristics was observed unobviously. The conversion of Ohmic to Schottky contacts might be fabricated with improving prepared ZnO and post-deposition annealing conditions. |
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