An Au/Indigotindisulfonate Sodium (IS)/n-Si/Al device was fabricated and the current-voltage measurements of the devices showed diode characteristics. Then the current-voltage (I-V), capacitance-voltage (C-V) and capacitance-frequency (C-f) characteristics of the device were investigated at room temperature. The values of various junction parameters such as ideality factor, barrier height, and series resistance were determined from the forward bias I-V characteristics, Cheung method, and Norde's function. The ideality factor of 1.73 and barrier height of 0.83 eV were calculated using current-voltage characteristics. It has been seen that the IS layer increases the effective barrier height of the structure because this layer creates the physical barrier between the metal and the semiconductor. The lower values of capacitance at high frequencies were attributed to the excess capacitance resulting from the interface states in equilibrium with the n-Si that cannot follow the alternating current (ac) signal. (C) 2010 Elsevier Ltd. All rights reserved.