Figure 10

Calibration details. (a) Schematic of the GaAs/AlGaAs heterostructure below the surface-gate defined QPC (yellow) with indications on the surface charges (red circles), Si dopants (blue circles) and the 2DEG (red line). (b) Scanning-electron-microscopy image of a QPC design. (c) Experimental current I across the narrow constriction as a function of the surface-gate voltage \(V_{\mathrm{G}}\). (d) Simulated distribution of the electron density \(n_{\mathrm{2DEG}}\) for \(V_{\mathrm{G}}=-1.80\text{ V}\) using nextnano. The grey polygons correspond to the gate geometry. (e) Electron density \(n_{\mathrm{2DEG}}\) along the constriction (\(y=0\); dashed line in (d)) for three values of \(V_{\mathrm{G}}\). (f) Electron density \(n_{\mathrm{2DEG}}\) below the surface gate (black square) and at the middle of the constriction (red circle). The simulated QPC pinch-off occurs when the 2DEG is completely depleted