Electrical properties of rectifying contacts on selectively carrier controlled grown ZnO thin films

Abstract

Controlled decrease in carrier concentration (Nd) through postdeposition annealing of ZnO is shown to provide a crossover from Ohmic to rectifying junction behavior. Highly oriented (002) ZnO films with silver contact yield nonlinear I-V characteristics below a carrier concentration of ∼1023 m−3 and linear Ohmic behavior above 1023 m−3. The specific differential resistance around zero bias is practically independent of carrier concentration up to 1023 m−3 and then decreases with increase in carrier concentration. These results are in excellent agreement with standard theoretical models of current transport phenomena in metal–semiconductor contacts. While the differential junction resistance at lower carrier concentrations gradually becomes less governed by carrier concentrations and current transport is dominated by thermionic emission and diffusion mechanism, it decreases as a function of carrier concentration at higher carrier concentrations. These results show that metal–oxide semiconductor junctions b...