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We fabricated an etched hole quantum dot in a Si-doped (311)A AlGaAs/GaAs heterostructure to study disorder effects via magnetoconductance fluctuations (MCF) at millikelvin temperatures. Recent experiments in electron quantum dots have shown that the MCF is sensitive to the disorder potential created by remote ionised impurities. We utilize this to study the temporal/thermal stability of Si acceptors in p-type AlGaAs/GaAs heterostructures. In particular, we use a surface gate to cause charge migration between Si acceptor sites at T = 40 mK, and detect the ensuing changes in the disorder potential using the MCF. We show that Si acceptors are metastable at T = 40 mK and that raising the device to a temperature T = 4.2 K and returning to T = 40 mK is sufficient to produce complete decorrelation of the MCF. The same decorrelation occurs at T ~ 165 K for electron quantum dots; by comparing with the known trap energy for Si DX centers, we estimate that the shallow acceptor traps in our heterostructures have an activation energy EA ~ 3 meV. Our method can be used to study charge noise and dopant stability towards optimisation of semiconductor materials and devices.
We carry out microphotoluminescence measurements of an acceptor-bound exciton (A^0X) recombination in the applied magnetic field with a single impurity resolution. In order to describe the obtained spectra we develop a theoretical model taking into a
We report the observation of Coulomb blockade in a quantum dot contacted by two quantum point contacts each with a single fully-transmitting mode, a system previously thought to be well described without invoking Coulomb interactions. At temperatures
Low-temperature transport properties of a lateral quantum dot formed by overlaying finger gates in a clean one-dimensional channel are investigated. Continuous and periodic oscillations superimposed upon ballistic conductance steps are observed, when
We study the Zeeman splitting in lateral quantum dots that are defined in GaAs-AlGaAs het- erostructures by means of split gates. We demonstrate a non-linear dependence of the splitting on magnetic field and its substantial variations from dot to dot
We study a quantum dot connected to the bulk by single-mode junctions at almost perfect conductance. Although the average charge $elangle N rangle$ of the dot is not discrete, its spin remains quantized: $s=1/2$ or $s=0$, depending (periodically) on