The junction characteristics of the organic compound methyl-red film (2-[4-(dimethylamino)phenylazo]benzoic acid) on a p-type Si substrate have been studied. The current-voltage characteristics of the device have rectifying behavior with a potential barrier formed at the interface. The barrier height and ideality factor values of 0.73 eV and 3.22 for the structure have been obtained from the forward bias current-voltage (I-V) characteristics. The interface state energy distribution and their relaxation time have ranged from 1.68 x 10(12) cm(-2) eV(-1) and 1.68 x 10(-3) s in (0.73-E-v) eV to 1.80 x 10(12) cm(-2) eV(-1) and 5.29 x 10(-5) s in (0.43-E-v) eV, respectively, from the forward bias capacitance-frequency and conductance-frequency characteristics. Furthermore, the relaxation time of the interface states shows an exponential rise with bias from (0.43-E-v) eV towards (0.73-Ev) eV. (C) 2007 Elsevier B.V. All rights reserved.