Analytical modeling of surface-potential and drain current in AlGaAs/GaAs HEMT devices

We present an analytical calculation for the surface-potential and a surface-potential-based drain current model in AlGaAs/GaAs HEMT devices. We have developed a precise analytical calculation for the position of the Fermi level E_f in these devices from a consistent solution of Schrödinger´s and Poisson´s equations. The accuracy of our calculation is of the order of pico-volts. E_f is used to define the surface-potential ψ and subsequently derive the drain current I_d. Real device effects like mobility degradation, velocity-saturation, channel-length modulation and self-heating are included in the model. The model is in excellent agreement with experimental data.