The diode ideality factor is an important parameter in the description of device's electrical behavior. Our goal in this work is to find a practical Procedure for determination of diode ideality factors of heterojunction devices which contain parallel connected diodes series with resistance in the equivalent circuit. For this purpose, Beta (beta) model is applied to experimental current-voltage (I-V) data of the heterojunction (wenrun 10 mm white LED) structure. Diodes' ideality factors are easily determined by using beta model. This model lights on potential barrier number in the device without making any additional experimental measurements. Analyzing the LED's I-V curves with the help of beta model shows the ideality factors larger than unity to result from lateral fluctuations of the local characteristic tunneling energies. Results obtained from beta model are consistent with experimental data. (C) 2008 Elsevier B.V. All rights reserved.