Electron transfer efficiency of Si δ-modulation-doped pseudomorphic GaAs/In_0.2Ga_0.8As/Al_xGa_1-xAs quantum wells

In Si δ-modulation-doped GaAs/In_0.2Ga_0.8As/Al_xGa_1-xAs quantum well structures (QWs), the electrons from the ionized Si donors are initially confined in the V-shaped potential well (V-PW) formed at the position of a Si δ-doped layer. The efficiency of electrons transferring from the V-PW to the QW was investigated as a function of Si δ-doping concentration in the symmetric GaAs/In_0.2Ga_0.8As/GaAs QW at 1.7 K. The electron density in the QW increases linearly with an increase of Si δ-doping concentration, while the electron transfer efficiency remains unchanged either in the dark or under the illumination. The asymmetric GaAs/In_0.2Ga_0.8As/Al_0.2Ga_0.8As QW has a relatively higher electron transfer efficiency. The effect of grading the Al mole fraction over the Al_xGa_1-xAs spacer layer on the electron transfer efficiency was also reported.