A comparison of nine different nonlinear I-V models for the simulation of subinicron GaAs MESFET dc characteristics has been made. Drain-to-source current, I-ds as a function of gate-to-source, V-gs and drain-to-source, V-ds, voltages has been simulated and then compared with experimental data. To determine the accuracy of a model, root-mean-square (RMS) errors were calculated. The lowest RMS error was observed for Ahmed model whereas it was highest for Statz model. An ideal Schottky barrier junction free from interface states has been assumed in these models and thus their applications in device simulation are limited. To simulate output characteristics of a GaAs MESFET having finite density of sates at Schottky barrier, Ahmed model has been modified. It has been demonstrated that the proposed model is a comprehensive one and can simulate the device characteristics, with significant improved accuracy, for varying Schottky barrier conditions. (c) 2007 Elsevier Ltd. All rights reserved.