Assessment of quantum point contact stability in GaAs/AlGaAs heterostructures with trench gates

GaAs/AlGaAs heterostructures designed to probe fragile quantum Hall states in the 2nd Landau level typically suffer from poor gate stability. We study the stability and edge mode transmission of quantum point contacts utilizing etched trenches and low temperature illumination. We observe that devices etched past the doping layer above the quantum well show low hysteresis and conductance drift after an initial burn-in sweep of the gate voltage. Nevertheless, the electron density within the constriction is typically reduced from the bulk value after the burn-in process. We report on fabrication and gate operation techniques to reduce this density difference.