Ultrasmall nanoscale devices fabricated from compensating-layer GaAs/AlGaAs heterostructures

Nanoscale devices are fabricated from modulation-doped GaAs/AlGaAs heterostructures, where the two-dimensional electron system is initially depleted. Upon removing the p-type capping layer that compensates for the n-type supply layer, the electron system is induced. Arbitrarily shaped areal, line, and dot elements, i.e. the nanostructures and 2D leads, are simultaneously fabricated by patterning a thin resist layer with an atomic force microscope and subsequent selective wet etching. In this way a single-electron transistor (SET) with a 60 nm diameter island, a 60 nm wide electron waveguide (EWG), and an Aharonov–Bohm (AB) loop of 110 nm average diameter are prepared. Measurements at T=1.5 K reveal Coulomb-blockade, quantized conductance and AB-oscillations for the SET, EWG, and AB loop, respectively. Finally, an EWG is demonstrated in split-gate geometry where the compensating layer is used as split gate.