REDUCED INTERVALLEY SCATTERING RATES IN STRAINED SI/SIXGE1-X QUANTUM-WELLS AND ENHANCEMENT OF ELECTRON-MOBILITY - A MODEL CALCULATION

In a Si/Si0.5Ge0.5 quantum well grown on a [100] oriented Si0.75Ge0.25 buffer, the four valleys having longitudinal mass normal to the [100] direction are lifted from the remaining two valleys. As a consequence, the intervalley f scattering between these two groups of valleys, the strongest in bulk Si, occurs only when the electrons in the subbands reach a high threshold energy. A high value of mobility limited mainly by acoustic phonon scattering is thus expected and is also obtained from the model calculation described in the present work. It is shown that higher values of the mobility may be obtained for wider wells.