Abstract
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 are sensitive to the disorder potential created by remote ionized 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 $T\ensuremath{\sim}165$ 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 ${E}_{A}\ensuremath{\sim}3$ meV. Our method can be used to study charge noise and dopant stability towards optimization of semiconductor materials and devices.
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