Temperature Dependence of Magnetocapacitance in n-AlGaAs/GaAs Selectively Doped Heterojunction with InGaAs Quantum Dots

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The magnetocapacitance between a two-dimensional electron gas (2DEG) and a gate electrode has been studied in a selectively doped n-AlGaAs/GaAs heterojunction in which InGaAs quantum dots (QDs) are embedded in the vicinity of a GaAs channel. By comparing the experimental results with a resistive plate model, we have estimated the frequency $f$ dependence of the bulk conductance $\sigma_{xx}$ of the 2DEG in a quantum Hall regime and found that $\sigma_{xx}$ is well fitted by the form $\sigma_{\text{dc}} + A f^{S}$. We have also examined $\sigma_{\text{dc}}$, $A$, and $S$ as functions of temperature $T$. It was found that the dc part $\sigma_{\text{dc}}$ is well described as $\sigma_{0}\exp[-(T_{0}/T)^{2}]$ in the conduction of variable range hopping. It was also found that $A$ is proportional to $T^{n}$ ($n \sim 6.4$), while $S$ behaves as $1 - CT$ ($C \sim 1.35$), which can be explained by the pair approximation.
2010-09-25