Fabrication and characterization of NiO/ZnO p–n junctions by pulsed laser deposition

Transparent and conducting ZnO and NiO films were used for fabrication of p–n junction by pulsed laser deposition. These films were characterized by X-ray diffraction (XRD), atomic force microscopy, UV–visible spectroscopy, and electrical techniques. XRD shows that ZnO films are highly orientated along the (0 0 2) direction, while NiO films have preferred orientation along the (1 1 1) direction. These films are very smooth with surface roughness of ∼1.2 nm. The optical transmittances of ZnO and NiO films are 87% and 64%, respectively. I–V characteristics of the ZnO–NiO junction show rectification. The junction parameters such as ideality factor, barrier height, and series resistance are determined using conventional forward bias I–V characteristics, the Cheung method, and Norde's function. There is a good agreement between the diode parameters obtained from these methods. The ideality factor of ∼4.1 and barrier height of ∼0.33 eV are estimated using current–voltage characteristics.