An analytical two-dimensional model for AlGaN/GaN modulation-doped field effect transistor is developed. The spontaneous and piezoelectric polarization effects have been included. Two-dimensional analysis has been carried out in the high field region. The output characteristics, device transconductance and cut off frequency for 120 nm gate length device are obtained. Peak transconductance of 320 mS/mm and a cut off frequency of 120 GHz has been obtained. The results show excellent agreement when compared with experimental data thereby proving the validity of the model. (C) 2007 Elsevier Ltd. All rights reserved.