Evaluation of ZnO Films by I-V Characteristics of SIS Structures

Abstract

The n-ZnO/SiO2/n-Si and n-ZnO/SiO2/p+-Si (SIS) structures were fabricated by using a pulsed laser deposition (PLD) technique under various temperatures and oxygen ambient pressures. All the I-V characteristics showed typical rectifying behaviors. For the specimens fabricated under various temperatures, the near-band-edge (NBE) emission intensity of photoluminescence (PL) spectra had a maximum value for the ZnO layer fabricated at 650°C. The slope of the forward current of the SIS structure also had a maximum value for the ZnO layer fabricated at 650°C. These results suggest that 650°C was the optimum growth temperature for the ZnO layer. For the specimens fabricated under various oxygen pressures, the NBE emission intensity of PL spectra had a maximum value for the ZnO layer fabricated under 0.01 Torr. As the oxygen pressure was increased, however, the red-band (RB) emission intensity was decreased and the green-band (GB) emission intensity was increased. For the I-V characteristics, as the oxygen pressure was increased, the slope of the forward current was slightly decreased and the threshold voltage was increased. These results imply that the optimum oxygen pressure was around 0.01 Torr for the ZnO layer but it could vary between 0.01 and 0.07 Torr.