2-D semiconductors show great promise to serve as channel materials in next-generation field-effect transistors (FETs). The permittivity of many 2-D semiconductors is anisotropic, though many recent simulation works studying 2-D FETs have treated these materials as though they have isotropic permittivities. Because there have been no works that investigate the role of each element of a semiconductor’s anisotropic permittivity on a device’s performance, the impact that this isotropic approximation has on a simulation’s accuracy is unknown. Furthermore, the impact of a semiconductor’s anisotropic permittivity on a device’s performance cannot be explained using existing theory. In this simulation study, we investigate, for the first time, the impact of a semiconductor’s anisotropic permittivity on the performance of FETs. Our main findings are that the isotropic approximation becomes inaccurate as the channel lengths of FETs are scaled down and that short-channel effects become less significant when the semiconductor’s in-plane permittivity decreases or its out-of-plane permittivity increases. We also find that the capacitance of the semiconductor in the out-of-plane direction (i.e., the capacitance associated with the out-of-plane permittivity) more significantly influences a device’s gate capacitance when equivalent oxide thickness (EOT) decreases. Therefore, EOT alone cannot be used to assess total gate control in aggressively scaled 2-D devices.

中文翻译：

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评估半导体各向异性介电常数在二硫化铪单层场效应晶体管中的作用

二维半导体显示出作为下一代场效应晶体管 (FET) 通道材料的巨大希望。许多二维半导体的介电常数是各向异性的，尽管最近许多研究二维 FET 的模拟工作已将这些材料视为具有各向同性的介电常数。因为还没有研究半导体各向异性介电常数的每个元素对器件性能的作用的工作，所以这种各向同性近似对模拟精度的影响是未知的。此外，使用现有理论无法解释半导体的各向异性介电常数对器件性能的影响。在这项模拟研究中，我们首次研究了半导体的各向异性介电常数对 FET 性能的影响。我们的主要发现是，随着 FET 的沟道长度按比例缩小，各向同性近似变得不准确，并且当半导体的面内介电常数降低或面外介电常数增加时，短沟道效应变得不那么显着。我们还发现，当等效氧化物厚度 (EOT) 减小时，半导体在面外方向上的电容（即与面外介电常数相关的电容）对器件的栅极电容影响更大。因此，不能单独使用 EOT 来评估积极缩放的 2-D 器件中的总栅极控制。