Understanding the improved performance of strained Si/Si_1-xGe_x channel MOSFETs

We have studied in depth the performance of superficial strained Si/Si_1-xGe_x channel MOSFETs. To do so, we developed a two-dimensional drift-diffusion simulator including inversion layer quantization and low-field mobility curves obtained by means of a Monte Carlo simulator. We have reproduced experimental results. The dependences of the performance enhancement obtained in these devices on the germanium mole fraction, the drain-source and gate-source voltages are described in depth. At high-longitudinal electric fields the transconductance improvement is reduced due to the common value of the saturation velocity for all the different germanium mole fractions.