A 2-D analytical thermal model for the I-V characteristics of AlGaN/GaN is presented. The effect of self-heating is studied by investigating the temperature effects on various parameters: the 2DEG sheet carrier density. the Fermi level, the electron mobility, the saturation velocity and the critical field. After incorporating self-heating effect in calculations of current-voltage characteristics, our results agreed well with published experimental data. (C) 2009 Elsevier Ltd. All rights reserved.