Subband electron densities of Si δ-doped pseudomorphic In0.2Ga0.8As/GaAs heterostructures

Abstract

Magnetotransport properties of Si δ-doped pseudomorphic In0.2Ga0.8As/GaAs heterostructures grown by metalorganic vapor phase epitaxy have been investigated in magnetic fields up to 12 T in the dark at 1.7 K. Different δ-doping configurations, in which the same Si δ-doped layer was placed at different positions with respect to the In0.2Ga0.8As well, have been studied to clarify their effect on subband electron densities in the well. Very high electron densities of >4×1012 cm−2 were obtained when placing a Si δ-doped layer at the well center or the well–barrier interface. We found that one subband was occupied in the well-center-doped structure, but when the Si δ-doped layer was at the well–barrier interface, the second subband in the well became occupied. The electron density of Si δ-modulation-doped In0.2Ga0.8As/GaAs heterostructures, in which the cap barrier or the buffer barrier was Si δ doped, was in the order of <1.2×1012 cm−2. The Si δ doping in both of the barriers led to an increase of the electron density by almost a factor of 2. Owing to an incomplete transfer of the electrons from the Si δ-doped layers to the well, parallel conduction was observed in the Si δ-modulation-doped structures.