Screening effects of superlattice doping on the mobility of GaAs two-dimensional electron system revealed by in-situ gate control

We investigate the screening effects of excess electrons in the doped layer on the mobility of a GaAs two-dimensional electron system (2DES) with a modern architecture using short-period superlattice (SL) doping. By controlling the density of excess electrons in the SL with a top gate while keeping the 2DES density constant with a back gate, we are able to compare 2DESs with the same density but different degrees of screening using one sample. Using a field-penetration technique and circuit-model analysis, we determine the density of states and excess electron density in the SL, quantities directly linked to the screening capability. The obtained relation between mobility and excess electron density is consistent with the theory taking into account the screening by the excess electrons in the SL. The quantum lifetime determined from Shubnikov-de Haas oscillations is much lower than expected from theory and did not show a discernible change with excess electron density.