Strain-induced disorder from Schottky gates on high mobility 2DEGs
Electrostatic gates on two-dimensional electron gases (2DEGs) in GaAs/AlGaAs heterostructures are essential for numerous studies of correlation driven phenomena, many performed within the fractional quantum Hall effect. However, the most commonly used type of gates, the metallic Schottky gate, has the propensity to adversely impact the electron mobility and suppress the fractional quantum Hall states. Here we demonstrate through commensurability oscillations under specially designed nanostructured superlattice gates, that strain effects are responsible for the mobility reduction. The experimental results agree well with COMSOL Multiphysics simulations. In a regular, unpatterned gate the disordered, granular nature of the metal film fills the same role as the superlattice in creating a strain field penetrating down to the 2DEG, as we show with a simplified model. These results will help in understanding, improving and finding novel methods to reduce strain-induced disorder in gated high-mobility 2DEGs.