一个非晶InGaZnO薄膜晶体管线性区陷阱态的提取方法

非晶InGaZnO(a-IGZO)薄膜在制备过程中形成的缺陷和弱键以陷阱态的形式非均匀分布在a-IGZO的带隙中, 这些陷阱态会俘获栅压诱导的电荷, 影响a-IGZO薄膜晶体管线性区迁移率、沟道电子浓度等, 进而影响线性区的电学性能. 本文基于线性区沟道迁移率与沟道内的自由电荷与总电荷的比值成正比, 分离出自由电荷以及陷阱态电荷. 由转移特性和电容电压特性得到自由电荷以及陷阱态电荷对表面势的微分, 分离出自由电子浓度和陷阱态浓度. 通过对沟道层与栅绝缘层界面运用泊松方程以及高斯定理, 考虑了沟道表面势与栅压的非均匀性关系, 得出自由电子浓度以及陷阱态浓度与表面势的关系, 最后通过陷阱态浓度与表面势求导得到线性区对应的态密度.     

Electronic states and spin-filter effect in three-dimensional topological insulator Bi_2Se_3 nanoribbons

We study the electronic band structure, density distribution, and transport of a Bi_2Se_3 nanoribbon. We find that the density distribution of the surface states is dependent on not only the shape and size of the transverse cross section of the nanoribbon, but also the energy of the electron. We demonstrate that a transverse electric field can eliminate the coupling between surface states on the walls of the nanoribbon, remove the gap of the surface states, and restore the quantum spin Hall effects. In addition, we study the spin-dependent transport property of the surface states transmitting from top and bottom surfaces(x-y plane) to the side surfaces(z-x plane) of a Bi_2Se_3 nanoribbon. We find that transverse electric fields can open two surface channels for spin-up and-down Dirac electrons, and then switch off one channel for the spin-up Dirac electron. Our results may provide a simple way for the design of a spin filter based on topological insulator nanostructures.