Investigation of Si/SiGe-based FET geometries for high frequency performance by computer simulation

The high frequency performance of n-channel Si/SiGe-based FETs is investigated by computer simulation. Using a two-dimensional hydrodynamic model, devices having gate lengths down to 0.1 /spl mu/m are examined. Self-aligned heterojunction MOSFETs are found to offer the best performance in terms of cut-off frequency and available voltage gain. Schottky gate heterojunction FETs have the highest transconductance in this study, but simulations confirm that this is because of the close proximity of the channel to the gate. Depletion mode MOS gate devices are also considered and a large parameter space is explored.