Influence of (formula presented) doping position on subband properties in (formula presented) heterostructures

Subband properties of Si (formula presented) heterostructures have been investigated by solving the Schrödinger-Kohn-Sham equation and the Poission equation self-consistently, and by the density-density dynamical response function. The shift of the same Si (formula presented)-doped layer from the quantum-well center (the origin is at (formula presented) to the barrier (formula presented) has been studied to find its effect on subband electron densities and mobilities. The electron density of the first subband is greater than (formula presented) when a (formula presented) is placed in the well. It is only (formula presented) for the doping position with a (formula presented) spacer layer. The electron occupation of the second subband is 15.4% in the well-center-doped structure. It is up to the maximum of 42.3% at (formula presented) The electron mobility is not changed significantly for the first subband, but is varied noticeably for the second subband by moving the Si (formula presented) doping position in the well. The highest electron mobility is obtained at about (formula presented) for the first subband, and at about (formula presented) for the second subband. The calculated results are also compared to the corresponding experimental data.