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

Abstract

The $\mathrm{Ga}\mathrm{As}$/$(\text{Al,Ga})\mathrm{As}$ heterostructure with short-period superlattice (SPSL) doping possesses ultrahigh mobility of its two-dimensional electron gas by placing donors within the remote $\mathrm{Ga}\mathrm{As}$ 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 $5.9\mathrm{%}$. Meanwhile, the quantum lifetime ${\ensuremath{\tau}}_{q,\text{QW}}$ 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 ${\ensuremath{\tau}}_{q,\text{QW}}$ under illumination for the conventional doping situation. The increase of ${\ensuremath{\tau}}_{q,\text{QW}}$ originates from the larger donor filling-fraction-enhanced screening effect. Meanwhile, the decrease of ${\ensuremath{\tau}}_{q,\text{QW}}$ may be caused by stronger scattering of ionized ${d}^{+}$ states evolved from DX centers. The transfer of excess electrons between the $\mathrm{Al}\mathrm{As}$ layers can also cause the decrease of ${\ensuremath{\tau}}_{q,\text{QW}}$. This work provides an insight into the mechanism of DX centers on the quantum transport properties of SPSL-doped heterostructures.