An analytical model for 2 Dimensional Electron Gas (2-DEG) charge density in AlGaN/GaN High Electron Mobility Transistors is developed considering electron charge in the AlGaN barrier layer. Simplified Fermi-Dirac statistics are used to calculate the electron charge density in the AlGaN barrier. This model is valid for the entire range of operation from subthreshold to practical forward biases. The results from the model show an excellent match with simulation results from a numerical self-consistent Poisson-Schrodinger solver. The model correctly predicts the saturation of 2-DEG charge density at higher gate biases. © 2014 IEEE.