Van der Waals heterostructures provide a versatile tool to not only protect or control, but also enhance the properties of a 2D material. We use ab initio calculations and semianalytical models to find strategies which boost the mobility of a current-carrying two-dimensional (2D) semiconductor within a heterostructure. Free-carrier screening from a metallic “screener” layer remotely suppresses electron-phonon interactions in the current-carrying layer. This concept is most effective in 2D semiconductors whose scattering is dominated by screenable electron-phonon interactions, and in particular, the Fröhlich coupling to polar-optical phonons. Such materials are common and characterized by overall low mobilities in the small doping limit and much higher ones when the 2D material is doped enough for electron-phonon interactions to be screened by its own free carriers. We use GaSe as a prototype and place it in a heterostructure with doped graphene as the “screener” layer and boron nitride as a separator. We develop an approach to determine the electrostatic response of any heterostructure by combining the responses of the individual layers computed within density functional perturbation theory. Remote screening from graphene can suppress the long-wavelength Fröhlich interaction, leading to a consistently high mobility around $500–600{\mathrm{cm}}^2$/V s for carrier densities in GaSe from ${10}^{11}$ to ${10}^{13}{\mathrm{cm}}^{-2}$. Notably, the low-doping mobility is enhanced by a factor 2.5. This remote free-carrier screening is more efficient than more conventional manipulation of the dielectric environment, and it is most effective when the separator (boron nitride) is thin.

中文翻译：

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远程自由载流子筛选，以提高Fröhlich限制的二维半导体的迁移率

Van der Waals异质结构提供了一种多功能的工具，不仅可以保护或控制，还可以增强2D材料的性能。我们使用从头算和半分析模型来寻找可提高异质结构中载流二维（2D）半导体迁移率的策略。来自金属“屏蔽层”的自由载流子屏蔽可远程抑制载流层中的电子-声子相互作用。此概念在其散射主要由可屏蔽的2D半导体中最有效电子-声子相互作用，尤其是Fröhlich耦合到极光声子。这种材料很常见，其特点是在较低的掺杂极限下总体迁移率较低，而在对2D材料进行足够掺杂以使其自身的自由载流子屏蔽电子-声子相互作用时，迁移率则更高。我们将GaSe用作原型，并将其置于异质结构中，其中掺杂的石墨烯作为“屏蔽层”，而氮化硼作为隔离层。我们开发了一种方法，可以通过结合在密度泛函扰动理论中计算出的各个层的响应来确定任何异质结构的静电响应。从石墨烯进行远程筛选可以抑制长波长Fröhlich相互作用，从而导致始终如一的高迁移率$500–600{\mathrm{厘米}}^2$GaS中载流子密度的/ V s为 ${10}^{11}$ 到 ${10}^{13}{\mathrm{厘米}}^{-2}$。值得注意的是，低掺杂迁移率提高了2.5倍。这种远距离自由载流子筛选比介电环境的常规操作更有效，并且当隔离层（氮化硼）较薄时最有效。