Subband characteristics of Si δ-doped pseudomorphic In_0.2Ga_0.8As/GaAs heterostructures

Subband properties of Si δ-doped pseudomorphic In_0.2Ga_0.8As/GaAs 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. Different δ-doping configurations, in which the same Si δ-doped layer is placed at different positions with respect to the In_0.2Ga_0.8As well, have been studied to find their effect on subband electron densities and mobilities. High electron densities of greater than 3.6 × 10¹²cm^-2 are obtained when a δ-doping density of 4.5 × 10¹²cm^-2 is placed at the well center or at the well-barrier interface. However, the electron density in the well for Si δ-modulation-doped In_0.2Ga_0.8As/GaAs heterostructure is only about 1.3 × 10¹²cm^-2. The change of the position of a Si δ-doped layer from the well center to the barrier does not change the mobility of electrons in the lowest subband significantly. The Si δ doping in both barriers leads to an increase of the electron density by almost a factor of 2. The mobilities in the well for the modulation-doped structures are always much greater than those for the well-doped structures. The calculated results are also compared to the corresponding experimental data.