Role of deposition parameters on the properties of the fabricated heterojunction ZnS/p-Si Schottky diode

Abstract

Heterojunction diodes of ZnS/p-Si have been fabricated using the chemical bath deposition (CBD) technique at two different deposition durations under both stirring and non-stirring conditions. The x-ray diffraction (XRD) patterns indicate the deposited ZnS films exhibit good crystallinity with the growth direction along the (111) planes of a cubic zinc blend structure. The crystallite size of all the deposited ZnS thin films have been calculated using the Scherer formula and found to be in the range of 2.2–2.7 nm which is very close (∼4 nm) to the size estimated using transmission electron microscopy (TEM). The surface morphology of the deposited ZnS thin films were studied by scanning electron microscopy (SEM) and it was observed that spherical nanoparticles agglomerated with the increase in deposition time. Furthermore, the optical properties of the deposited ZnS thin films were studied using UV-visible (UV-VIS) and photoluminescence (PL) spectroscopy. The effective calculated band gap was found in the range from 3.7–3.82 eV for all the samples, however PL spectra shows multiple emissions in the as-deposited ZnS films, indicating the presence of intrinsic defects, The characteristics of the fabricated ZnS/p-Si heterojunction diode was studied by measuring the dark current-voltage (I–V) relation using thermionic emission model. Electrical parameters such as barrier height, saturation current, ideality factor and series resistance were extracted from the I–V characteristics of the fabricated Schottky diodes. The barrier potential for all the ZnS/p-Si heterojunction diodes range between 0.829–0.857. Moreover, the calculated ideality factor was found very close to the ideal value of the diode (1.34 and 1.43) in the devices fabricated under stirring conditions.