Fabrication and electrical characterization of nanocrystalline ZnO/Si heterojunctions

Nanocrystalline zinc oxide (nc-ZnO) films were prepared by a sol–gel process on p-type single-crystalline Si substrates to fabricate nc-ZnO/p-Si heterojunctions. The structure and morphology of ZnO films on Si substrates, which were analyzed by X-ray diffraction (XRD) spectroscopy and atomic force microscopy (AFM), showed that ZnO films consisted of 50–100 nm polycrystalline nanograins with hexagonal wurtzite structure. The electrical transport properties of the nc-ZnO/p-Si heterojunctions were investigated by temperature-dependent current–voltage (I–V) measurements and room temperature capacitance– voltage measurements. The temperature-dependent I–V characteristics revealed that the forward conduction was determined by multi-step tunneling current, and the activation energy of saturation current was about 0.26 eV. The 1/C2–V plots indicated the junction was abrupt and the junction built-in potential was 1.49 V at room temperature