Fabrication and Characterization of the Ultrasmall Split Gate Type of GaAs Quantum Dots

초록

We present fabrication and electrical characterizations of the lithographically defined ultrasmall quantum dot device based on GaAs/AlGaAs heterostructure with a two-dimensional electron gas (2DEG) which is located 60nm beneath the surface. Quantum dot device, which is composed of fully tunable metal split gates, is defined by electron beam lithography technique. By adjusting the pinch-off gate voltages, electrical potential barriers are formed thus electrons are confined in an electronic island. Low temperature measurements of our device show a Coulomb blockade oscillation as a function of plunger gate voltages due to the quantum confinement and the electron charging effect. We obtain Coulomb diamond shapes of two dots from two-dimensional plots of conductance via gate and source-drain bias and find the charging energies of 2.2 and 4.41 meV, respectively. Large Coulomb energy gives a possibility of potential applications quantum dot devices functioning in high temperature condition.