Growth and temperature dependent characterization of pulsed laser deposited Ag/n-ZnO/p-Si/Al heterojunction

Abstract

The Ag/n-ZnO/p-Si(100)/Al heterojunction diodes were fabricated by pulsed laser deposition of zinc oxide (ZnO) thin films on p-type silicon. The X-ray diffraction analysis shows the formation of ZnO thin film with hexagonal structure having strong (002) plane as preferred orientation. The energy band gap of ZnO films simultaneously deposited on quartz substrate was calculated from the measured UV–Visible transmittance spectra. High purity vacuum evaporated silver and aluminum thin films were used to make contacts to the n-ZnO and p-silicon, respectively. The current–voltage and capacitance–voltage characteristics of Ag/n-ZnO/p-Si(100)/Al heterostructures were measured over the temperature range of 80–300 K. The Schottky barrier height and ideality factor were determined by fitting of the measured current–voltage data into thermionic emission diffusion equation. It is observed that the barrier height decreases and the ideality factor increases with decrease of temperature and the activation energy plot exhibit non-linear behavior. This decrease in barrier height and increase in ideality factor at low temperature are attributed to the occurrence Gaussian distribution of barrier heights. The capacitance–voltage characteristics of Ag/n-ZnO/p-Si(100)/Al heterojunction diode were also studied over the wide temperature range. Capacitance–voltage data are used to estimate the barrier height and impurity concentration in n-type ZnO.