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

Magnetotransport properties of Si delta-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 delta-doping configurations, in which the same Si delta-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 >4x10(12) cm(-2) were obtained when placing a Si delta-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 delta-doped layer was at the well-barrier interface, the second subband in the well became occupied. The electron density of Si delta-modulation-doped In0.2Ga0.8As/GaAs heterostructures, in which the cap barrier or the buffer barrier was Si delta doped, was in the order of <1.2x10(12) cm(-2). The Si delta 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 delta-doped layers to the well, parallel conduction was observed in the Si delta-modulation-doped structures. (C) 1997 American Institute of Physics.