QM/EM混合算法的发展及其在无接面场效应管模拟中的应用

Over the past few decades, the sizes of microelectronic devices have been reduced drastically following the Moore's Law. With this continuous miniaturization trend, the feature size of transistors is predicted to reach close to 10 nm in a few years. At this length scale, more and more fundamental changes become necessary for the design of new transistor devices. These changes include both device structures and simulation methodologies. It is necessary to incorporate quantum effects in device simulations. Currently, the existing field-effect transistors (FETs) are all based on the formation of junctions which control the flow of current through it by an applied gate voltage. For devices at nanoscale, this implies ultrasharp doping concentration gradients are required in junctions which imposes potential high cost of fabrication and limitations on the development. Recently, junctionless FETs made of silicon nanowire have been experimentally realized with a tri-gate structure. In the junctionless FETs, the doping concentration is identical across the device. The gradient of the doping concentration between source and channel or drain and channel thus vanishes. This eliminates the need for costly fabrication techniques and provides a potential candidate for the next generation electronic devices.. . To include quantum effects in the description of nanoscale electronic devices, a novel hybrid quantum mechanics/electromagnetics (QM/EM) method has been developed that combines the strengths of both QM (accuracy) and EM (efficiency) methods. In this project we propose to use the QM/EM method to model the junctionless FETs and calculate the corresponding I-V curves under different operation conditions. The resulting I-V curves can be used to construct the compact model that can in turn be used to calculate the electric responses under any operational conditions. Through the application of the QM/EM method to junctionless FETs, the proposed project aims to understand the underlining mechanism and improve the performance of junctionless FETs. In addition, the proposed project demonstrates a simulation approach for designing the next generation electronic devices.

电子元件的微型化一直遵循摩尔定律。以此趋势，几年内晶体管的尺寸将接近十纳米。届时现有的电子器件设计方法将不再适用，取而代之的将是全新的器件结构与仿真方法,量子效应将被纳入到模拟过程。..现有的晶体管都基于PN结。然而在纳米尺度上实现PN结，则面临着制造工艺及成本上的限制。最近，实验室里已经实现了三栅结构的硅纳米线制成的无接面晶体管。由于不存在PN结，设备的掺杂浓度是均匀的。这将极大的简化工艺，降低成本。因此无接面晶体管有望成为新一代的电子器件。..受QM/MM方法的启发，我们开发了一套量子力学/电磁学(QM/EM)混合算法，把量子力学的精确性和电磁学的高效性结合起来。在这里，我们将进一步发展该方法，并用于模拟无接面晶体管，计算其I-V曲线，进而构建简约模型。使用简约模型，我们可以在现有的电路模拟器上进行模拟，了解其工作机理并进行优化。该项目将首次实现从第一性原理到电子工程设计的跨越。

电子元件的微型化一直遵循摩尔定律。以此趋势，几年内晶体管的尺寸将接近十纳米。届时现有的电子器件设计方法将不再适用，取而代之的将是全新的器件结构与仿真方法,量子效应将被纳入到模拟过程。受QM/MM 方法的启发，我们开发了一套量子力学/电磁学(QM/EM)混合算法，把量子力学的精确性和电磁学的高效性结合起来。在本项目中，我们进一步发展了QM/EM方法，较大地提升了其模拟能力，准确性和计算效率。在方法论发展的基础上，我们将其应用到两个重要领域：1） 在原子层面模拟现实尺寸无接面晶体管，计算其IV曲线，进而构建简约模型。并使用该简约模型在现有的电路模拟器上进行模拟，了解其工作机理并进行优化。首次实现了从第一性原理到电子工程设计的跨越； 2）在量子力学层面模拟纳米光学器件。通过QM/EM频域算法以及声子-电子耦合作用，我们首次实现了第一性原理模拟真实条件下纳米光伏器件以及纳米发光二极管中的光电过程，在相关领域发展中迈出重要一步。本项目取得一系列有影响力的创新研究成果，在国际知名SCI期刊发表11篇论文。核心成员任志勇博士入选“青年千人”并获得国家自然科学基金委的“优秀青年科学基金”。