Fabrication and characterization of undoped and cobalt doped NiO-based diodes

In this study, undoped and cobalt-doped nickel oxide thin films were deposited on glass substrates and n-type silicon substrates by sol gel spin coating method. In the first step, the electrical conductivity of thin films, which was coated on glass substrates, was investigated. Then, heterojunction structures were produced by thin films coated on n-Si substrates. The forward and reverse current-voltage (I-V) characteristics of these heterojunction structures were investigated by using Thermionic Emission (TE) theory. It was observed that all fabricated structures exhibited rectification behavior. The basic electrical parameters of the diode such as ideality factor (n), barrier height (ΦB), rectification ratio (RR) and series resistance were calculated and compared. As a result of the measurements, the effect of cobalt doping on the fabricated heterojunctions was investigated. In addition, capacitance-voltage (C-V) and conductivity-voltage (G/w-V), series resistance-voltage (Rs-V) and interface states (Dit) graphs were plotted and analyzed in the frequency range of 10 kHz – 1 MHz. Electrical parametres of diodes such as Nd (cm-3), Vbi (eV), Nc (cm-3), Ef (eV), Փb (CV)Ev, Wd (nm), ∆Փb (eV) and Emax (V/cm) were calculated by using the capacitance values at 1 MHz. As a result of the calculations, it was observed that all electrical parameters were strongly dependent on the amount of dopant. In addition, this study shows that electrical parameters of diodes can be adjusted with cobalt doping.