Illumination effect on electrical characteristics of organic-based Schottky barrier diodes

The forward and reverse bias capacitance-voltage (C-V) and conductance-voltage (G/omega-V) characteristics of Au/polyvinyl alcohol (Co, Zn-doped)/n-Si Schottky barrier diodes have been investigated depending on illumination intensity at room temperature and 1 MHz. These experimental C-V and G/omega-V characteristics show fairly large illumination dispersion especially in the weak inversion and depletion regions and they increase with the increasing illumination intensity because of the illumination induced interface states and electron-hole pair. The C-V plots show that peaks are the results of the particular distribution density of the interface states (N-ss), interfacial polymer layer, and series resistance (R-s) of device. The magnitude of the peaks increases with the increasing illumination intensity and their positions shift from the high forward bias voltage to low forward bias voltages. The C-2-V plots give a straight line in a wide bias voltage region for each illumination intensity. The variation in doping concentration (N-D), depletion layer width (W-D), and barrier height [Phi(B)(C-V)] were obtained from these C-2-V plots. In addition, voltage dependent density distribution profile of N-ss was obtained from both low-high capacitance (C-LF -C-HF) and Hill-Coleman methods. It is observed that there is a good agreement between the results obtained by these methods. In addition, voltage dependent R-s profile was obtained from C-V and G/omega-V data by using Nicollian and Brews method. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3504598]