Magnetotransport properties of Yb-doped AlxGa1−xAs/GaAs two-dimensional electron systems

The magnetotransport properties of three different structured Yb-doped AlxGa1−xAs/GaAs two-dimensional electron systems (2DES) were investigated. The Al0.3Ga0.7As:Yb sample showed a clear integer quantum Hall effect (IQHE) irrespective of photoexcitation, whereas the AlAs:Yb samples showed a clear IQHE only under photoexcitation above 1.89 eV. Under a dark condition and photoexcitation below 1.89 eV, the resistance of the AlAs:Yb samples significantly increased in the high-magnetic-field region, suggesting that 2D electrons were scattered by the Yb-related electron trap. From the analysis of a band diagram, the Yb-related states in the AlAs:Yb and Al0.3Ga0.7As:Yb samples were estimated to be located below and above the GaAs conduction band edge, respectively, and the level of the Yb-related state was found to shift with the change in the energy band structure of the host material.