Mobility and quantum mobility of a 2DEG in modern GaAs/AlGaAs heterostructures

In modern GaAs/AlGaAs heterostructures with record high mobilities, a two-dimensional electron gas (2DEG) in a quantum well is provided by two remote donor δ-layers placed on both sides of the well. Each δ-layer is located within a narrow GaAs layer, flanked by narrow AlAs layers which capture excess electrons from donors but leave each of them localized in a compact dipole atom with a donor. These excess electrons minimize their Coulomb energy and screen the random potential of charged impurities. We developed a theory of this screening and used it to calculate both the mobility and the quantum mobility of the 2DEG.[1,2] Our results show that the remote donor limited mobilities strongly increase with the filling fraction of excess electrons, and the calculated mobilities drastically exceed the measured values. This suggests that the mobiliites are limited either by background charged impurities, or the weakening of screening by additional disorder in the doping layer such as roughness at the GaAs/AlAs interface or spreading of the donors outside of the δ-layer. [1] M. Sammon, M. A. Zudov, B. I. Shklovskii, Phys. Rev. Materials 2, 064604 (2018). [2] M. Sammon, Tianran Chen, B. I. Shklovskii, Phys. Rev. Materials 2, 104001 (2018).