Electron transport in Si/SiGe modulation-doped heterostructures using Monte Carlo simulation

The electron transport in two-dimensional gas formed in tensile-strained Si1−xGex/Si/Si1−xGex heterostructures is investigated using Monte Carlo simulation. First the electron mobility is studied in ungated modulation-doped structures. Calculation matches the experimental results very well over a wide range of electron densities. The mobility typically varies between 1100 cm2/V s in highly-doped structures and 2800 cm2/V s at low electron density. The mobility is shown to be significantly influenced by the thickness of the spacer layer separating the strained Si channel from the pulse-doped supply layers. Then the electron transport is investigated in a gated modulation-doped structure in which the contribution of parasitic paths is negligible. The mobility is shown to be higher than in comparable ungated structures and dependent on the gate voltage as a result of the electron density dependence of remote impurity screening.