Investigation of photo-induced effect on electrical properties of Au/PPy/n-Si (MPS) type schottky barrier diodes

Abstract

Au/PPy/n-Si (MPS) type Schottky barrier diodes (SBDs) were produced and their current–voltage (I–V) characteristics were measured in the positive and negative bias regions at 300 K. The basic electronic quantities such as reverse-saturation current (Io), ideality factor (n), zero-bias barrier height (ФB0), series (Rs) and shunt resistances (Rsh) were obtained by using I–V data in total darkness and illumination (100 W/m2). The values of these parameters were found as 7.79 × 10−9 A, 5.41, 0.75 eV, 1 kΩ and 130 MΩ in dark) and 4 × 10−9 A, 4.89, 0.77 eV, 0.9 kΩ and 1.02 MΩ under illumination), respectively. Also the energy density distribution behaviors of surface states (Nss) have been acquired by calculation of effective barrier height (Фe) and ideality factor n (V) depending on voltage in total darkness and illumination. The values of Nss show an exponentially increase from the mid-gap of Si to the lower part of conduction band (Ec) for two conditions. The possible current conduction mechanisms were determined by plotting of the double logarithmic I–V plots in the positive voltage zone and the value of current was found proportional to voltage (I∼Vm). The high values of n and Rs were ascribed to the certain density distribution of Nss localized at semiconductor/PPy interface, surface conditions, barrier inequality, the thickness of PPy interlayer and its roughness. The open-circuit voltage of the photodiode was found as 0.36 V under 100 W/m2 illumination level. This is evidence that the fabricated sample is very sensitive to illumination. Therefore, it can be put into practice in optoelectronic industries as a photodiode or solar cells.