Anomalous Screening Effect of Superlattice-Doped GaAs / (Al,Ga)As Heterostructures under Illumination

The GaAs/(Al,Ga)As heterostructure with short-period superlattice (SPSL) doping possesses ultrahigh mobility of its two-dimensional electron gas by placing donors within the remote GaAs layers. Here, we investigate its magnetotransport property under a heavily doped situation. After long enough illumination at cryogenic temperature, the change of the electron concentration inside the quantum well (QW) is only 5.9%. Meanwhile, the quantum lifetime τq,QW of the electron shows an anomalous behavior. It increases slightly and then exhibits an exponential decay until saturation. This is different from the monotonic increase of τq,QW under illumination for the conventional doping situation. The increase of τq,QW originates from the larger donor filling-fraction-enhanced screening effect. Meanwhile, the decrease of τq,QW may be caused by stronger scattering of ionized d+ states evolved from DX centers. The transfer of excess electrons between the AlAs layers can also cause the decrease of τq,QW. This work provides an insight into the mechanism of DX centers on the quantum transport properties of SPSL-doped heterostructures.