Most of the techniques have been developed to extract diode ideality factor utilize the one-exponential diode model. However, for a correct description of two linear regions in the log I-V (current-voltage) graph Of Unipolar devices, one-exponential diode model is not sufficient. We have derived a new model which is named Beta (beta) model for the calculation of diode ideality factor from dark current-voltage characteristic of the device (p-i-n device). Results obtained from our model are considerably in compliance with the experimental data. (c) 2008 Elsevier B.V. All rights reserved.