Ultra-low acoustic-phonon-limited mobility and giant phonon-drag thermopower in MgZnO/ZnO heterostructures

Abstract

We present numerical simulations of the acoustic-phonon-limited mobility, ${\mu }_{ac}$, and phonon-drag thermopower, $S^g$, in two-dimensional electron gases confined in MgZnO/ZnO heterostructures. The calculations are based on the Boltzmann equation and are made for temperatures in the range 0.3-20 K and sheet densities $0.5$-$30\times 10^{15}$ m${}^{-2}$. The theoretical estimations of ${\mu }_{ac}$ are in good agreement with the experiment without any adjustable parameters. We find that the magnitude of ${\mu }_{ac}$ is dramatically decreased in relation to GaAs based heterostructures. The phonon-drag thermopower, $S^g$, which according to Herring's expression is inversely proportional to ${\mu }_{ac}$ is severely increased exceeding 200 mV/K at $T=5$ K depending on sheet density. The giant values of $S^g$ lead to a strong improvement of the figure of merit $ZT$ at low temperatures. Our findings suggest that MgZnO/ZnO heterostructures can be candidates for good thermoelectric materials at cryogenic temperatures.

5 pages, 4 figures

References in corpus (1)

• Temperature dependent magnetotransport around $\nu$= 1/2 in ZnO heterostructures

Cited by in corpus (1)

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