1.6纳米厚双栅（100）硅纳米片中的电子输运：考虑声子限域和远程声子散射的理论研究
Electron transport in a 1.6~nm-thick double-gated (100) silicon nanosheet: A theoretical study accounting for phonon confinement and remote-phonon scattering
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中文总结 AI 辅助
本研究通过理论分析，探讨1.6纳米厚双栅硅纳米片的电子输运，考虑声子限域与远程声子散射，揭示了边界条件、IPPs散射对迁移率和饱和速度的影响，为相关场效应晶体管性能优化提供理论依据。
中文摘要 AI 辅助
我们从理论上研究了具有SiO2/HfO2栅堆叠的顶栅和底栅（100）1.6纳米厚硅纳米片中的电子输运，重点关注影响输运的本征物理过程：声子的限域以及界面混合等离激元-声子激发（IPPs或“远程声子”）的存在。能带结构采用局域经验赝势计算；采用近似弹性连续介质模型考虑声学声子的限域；采用介电连续介质极限处理IPPs。我们发现，电子迁移率会受到处理声子限域所选边界条件的显著影响。在SiO2/HfO2界面处声子被钳定、Si/SiO2界面处光学声子被钳定这一更符合实际的假设下，室温迁移率远小于采用弹性高温近似下体声子这一常见假设得到的结果。我们还发现，由于带撇子带的复杂结构，高场饱和速度显著低于其体材料值，这一现象过去已在Si反型层中被测量到，但从未得到理论解释。最后，我们发现IPPs散射确实会降低低场迁移率，但由于SiO2界面层的存在以及金属栅极的邻近效应，其影响程度较小。此外，通过使电子保持更“冷”的状态，IPPs散射会导致更高的饱和速度。因此，栅极绝缘堆叠中高κ材料的存在不应对基于硅纳米片的场效应晶体管的性能产生负面影响。
英文摘要
We study theoretically electron transport in an top-and bottom-gated (100) 1.6 nm-thin silicon nanosheet with SiO2/HfO2 gate stacks, focusing on the intrinsic physical processes that affect transport: the confinement of phonons and the presence of interface hybrid plasmon-phonon excitations (IPPs or `remote phonons'). The band structure is calculated using local empirical pseudopotentials; an approximated elastic continuum model is used to consider the confinement of acoustic phonons; the dielectric continuum limit is used to deal with the IPPs. We find that the electron mobility is affected significantly by the boundary conditions chosen to deal with phonon confinement. The more realistic assumption of phonons clamped at the SiO2/HfO2 interfaces and optical phonons at the Si/SiO2 interfaces results in a room temperature mobility much smaller than what is obtained using the common assumption of bulk phonons in the elastic, high-temperature approximation. We also find that, as a result of the complicated structure of the primed subbands, the high-field saturated velocity is significantly lower than its bulk value, as it had been measured in the past in the case of Si inversion layers but never explained theoretically. Finally, we find that IPP scattering does depress the low-field mobility but to a small extent, thanks to the presence of the interfacial SiO2 layers and to the proximity of the metal gates. Moreover, by keeping electrons `cooler', IPP scattering results in a higher saturated velocity. Therefore, the presence of high-kappa materials in the gate-insulator stacks should not affect negatively the performance of field effect transistors based on Si nanosheets.
