半导体p-n结在足够大的反向偏压下在界面处会发生电子从价带到导带的量子隧穿,利用这种带间隧穿机制已经开发了新型的隧穿晶体管，它有望取代传统金属-氧化物-半导体场效应晶体管,成为未来低功耗集成电路的基本单元。但是,在大规模应用隧穿晶体管之前有许多关键物理问题尚待解决,特别是带间隧穿的低效率严重制约了它的高性能应用。本项目旨在研究半导体缺陷态和界面态辅助带间隧穿以及相应的量子过程机理。从带间隧穿的量子原理出发,基于经验赝势理论建立隧穿晶体管的大规模(百万原子)“原子尺度”量子模拟方法;采用密度泛函理论及量子模拟方法研究带隙缺陷态辅助带间隧穿的量子力学机理;研究异质结隧穿晶体管中的界面态效应,探讨界面拓扑态的存在性及其对带间隧穿过程的作用机理。在缺陷态和界面态辅助带间隧穿机理的研究基础上提出设计高性能隧穿晶体管的新方案,解决当前隧穿晶体管研究中的根本困难, 以期解释和预言新型器件

Inter-band quantum tunneling will happen when a semiconductor p-n junction is in a certain backward bias condition. Tunnel field-effect transistors based on such inter-band tunneling are widely believed to replace the traditional metal-oxide-semiconductor field-effect transistors, as the building blocks of the next generation low-power integrated circuits. However, there are still many fundamental physical problems need to be solved before the large-scale application of the tunnel transistors. Especially, the very low inter-band tunneling efficiency sets a fundamental limit of the high performance application of the tunnel transistors. This project will study the quantum mechanism of semiconductor defect and interface state assisted inter-band tunneling. We will first develop a large-scale (million atom system) “atomistic” quantum mechanical simulation of tunnel field-effect transistors based on atomistic empirical pseudopotential theory. Then the quantum mechanism of band-gap defect state assisted inter-band tunneling will be thoroughly studied by density-functional theory and the quantum simulation method. And the effect of interface states of a heterojunction inter-band tunneling system will also be studied, including the existence of interface topological states and their effects on inter-band tunneling. Finally we will present some physical approaches to optimize the performance of tunnel transistors based on the understanding of defect and interface state assisted inter-band tunneling. This is in a way to solve the fundamental problems in tunnel transistors, to explain and predict novel device physics, as well as to guide the development of novel semiconductor devices.