Current-Transport Mechanisms of the Al/(Bi2S3-PVA Nanocomposite)/p-Si Schottky Diodes in the Temperature Range Between 220K and 380K

摘要

In this research, bismuth sulfide nanostructures were prepared in the presence of polyvinyl alcohol (PVA) as a capping agent by an ultrasound-assisted method. The x-ray diffraction results show the crystalline phase of the sample and the mean crystalline size estimated by Debye-Scherer's equation. The UV-Vis absorption spectrum show that the optical absorbance edge of Bi2S3 nanostructure was blue-shifted. The Fourier transform infrared spectra confirm the presence of PVA in the sample and transmission electron microscopy imaging shows that the structures are in nanoscale. The semi-logarithmic forward bias I-V plots have two distinct linear regimes for each temperature which are called low- and moderate-bias regions (LBR and MBR). In order to effectively interpret possible current-conduction/transport mechanisms, the reverse saturation current (I-o), ideality factor (n) and zero-bias barrier height (phi(BO)) were obtained from the slope and intercept of these plots and they were found to be a strong function of temperature and voltage. The high value of n even at high temperature and the increase of phi(BO) with increasing temperature for the two regions is clear evidence of the deviation from thermionic emission (TE) theory. Therefore, phi(BO) versus n and q/2kT plots were drawn to get evidence of the Gaussian distribution (GD) of the barrier height (BH) and they show a linear behavior. The mean values of BH phi BO and standard deviation (sigma(s)) were also obtained from the intercepts and slopes of the phi(BO) versus q/2kT plots as 1.44 eV and 0.19 V for the LBR and 1.32 eV and 0.18 V for the MBR, respectively. After that, the values phi BO documentclass [12pt]{-69pt} and effective Richardson constant (A(*)) were obtained as 1.29 eV and 267.6A/(cm K)(2) for the LBR and 1.27eV and 281.7A/(cm K)(2) for the MBR, respectively. Such non-ideal I-V-T characteristics for the Al/(PVA-Bi2S3)/p-Si structure can be successfully explained by the single GD of BH for the LBR and MBR.