A fully 2-dimensional, quantum mechanical calculation of short-channel and drain induced barrier lowering effects in HEMTs

We have performed a fully 2-dimensional (2D) Poisson, Schrödinger and continuity equations modeling of nanometer gate HEMTs. For the electron density n(x, y) in the channel we use the discrete levels obtained from the Schrödinger equation and the corresponding 1D density of states (DOS), so that a fully quantum representation of n is obtained. The threshold voltage reduction ΔVT we obtain at small VDS is in very good agreement with experimental values. By comparison with our classical calculations (a subset of our model) we deduce that quantum effects are not important for the calculation of ΔVT. However quantum effects become increasingly important as VGS increases beyond VT at small VDS .The deviation between classical and quantum values in the current are of the order of 40–80% depending on the device. As VDS increases and reaches saturation this percentage deviation decreases but its absolute value (in mA/mm) increases. These effects become more acute as the gate length becomes shorter.