MgZnO/ZnO异质结构中的超低声学声子限制迁移率和巨声子拖曳热电势
Ultra-low acoustic-phonon-limited mobility and giant phonon-drag thermopower in MgZnO/ZnO heterostructures
摘要：
我们提出了数值模拟的声学声子有限的迁移率，$μ_{ac}$，声子拖曳热电势，$S^{g}$，在二维电子气限制在MgZnO/ZnO异质结构。计算是基于玻尔兹曼方程，并且是针对0.3-20 K范围内的温度和片材密度$0.5$ - $30\times 10^{15}$ m $^{-2}$进行的。在没有任何可调参数的情况下，$μ_{ac}$的理论估计值与实验值符合得很好。我们发现，$μ_{ac}$的幅度显着降低GaAs基异质结构。声子拖曳热电势$S^{g}$，根据Herring的表达式与$μ_{ac}$成反比，在$T=5$ K下严重增加超过200 mV/K，这取决于片密度。$S^{g}$的巨大值导致$ZT$在低温下的品质因数的强烈改善。我们的研究结果表明，MgZnO/ZnO异质结构可以在低温下良好的热电材料的候选人。
英文摘要：
We present numerical simulations of the acoustic-phonon-limited mobility, $μ_{ac}$, 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 $μ_{ac}$ are in good agreement with the experiment without any adjustable parameters. We find that the magnitude of $μ_{ac}$ 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 $μ_{ac}$ 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.
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