Experimental evidence for screening effects from surface states in GaAs/AlGaAs based nanostructures

We performed low-temperature conductance measurements on a lateral quantum dot device which is electrostatically defined by a split-gate and two overlaying finger gates which introduce tunnel barriers. The observed abrupt change in the measured Coulomb oscillations period is ascribed to the presence of the surface states. Using a simple model, we estimate the surface density of states in our system to be View the MathML source. This value is an order of magnitude lower than that in a GaAs/AlGaAs two-dimensional electron system. Our studies provide the first non-invasive measurements of the surface density of states in a GaAs system.