半导体径向异质结构纳米线器件中隧穿相关性能的优化

Radial heterostructure is a typical structure in nanowire devices. Quantum tunneling plays a key role during their operation, and it is therefore an important factor in improvement of the performance. In this proposal，theoretical models based on effective mass approximation will be established, for systematically investigating the tunneling transport of carriers in cylindrical and prism radial heterostructure nanowires. The discussed crystal structures will include zincblende, wurtzite and zincblende (or cubic rock salt)/wurtzite. The tunneling coefficients, time dependent properties as well as the modulation behaviors by geometric parameters (such as radius and/or cross section shape) and external conditions (such as strain or electric field) will be calculated, and accordingly tunneling current-voltage curves will be finally obtained. Furthermore, the tunneling properties in radial heterostructure nanowire of zincblende and wurtzite structure will be compared. The effects of spontaneous and piezoelectric polarizations in wurtzite structure on electronic resonant states and accordingly tunnel properties will also be discussed. Besides, considering the fine structure of optical phonons deduced by mixed crystal effects, the assistant mechanisms from each kind of optical phonons and their contributions to tunneling current will be clarified. In this proposal, the physical mechanisms of tunneling in radial heterostructure nanowire will be explored, aiming to offer a guidance for optimization of carrier tunneling related properties in nanowire devices.

径向异质结是半导体纳米线器件的典型结构，量子隧穿效应对此类器件的主要性能有重要作用。本项目拟采用有效质量近似，理论建模并系统研究圆柱及棱柱型径向异质结构纳米线中载流子的隧穿输运特性。拟讨论的纳米线晶体结构包括闪锌矿、纤锌矿以及闪锌矿（盐矿）/纤锌矿。探索上述径向异质结构纳米线中的载流子隧穿概率和穿越二维势垒的时间特性，及其随半径、截面形状等几何参数和应变、外电场等外界条件的变化规律，获得隧穿电流-电压特性曲线。进而，对比闪锌矿（各向同性）和纤锌矿（各向异性）纳米线中的隧穿特性，讨论纤锌矿的自发极化和压电极化效应对电子共振态乃至对隧穿性质的影响。此外，考虑混晶效应导致的光学声子精细结构，澄清各模式光学声子对载流子的辅助隧穿机制、对总电流的贡献及其调控规律。本研究探索径向异质结构纳米线中隧穿的物理机制，期待为半导体纳米线器件中载流子隧穿相关的性能优化提供理论依据。

本项目采用有效质量近似，理论建模并系统研究圆柱及棱柱型径向异质结构纳米线中载流子的隧穿输运特性. 讨论的纳米线晶体结构包括闪锌矿、纤锌矿以及闪锌矿（盐矿）/纤锌矿. 探索上述径向异质结构纳米线中的载流子隧穿概率及其随半径、截面形状等几何参数和应变等变化规律，获得隧穿电流-电压特性曲线. 讨论纤锌矿的自发极化和压电极化效应对电子共振态乃至对隧穿性质的影响. 此外，考虑混晶效应导致的光学声子精细结构，澄清各模式光学声子对载流子的散射作用. 结果显示，核壳结构纳米线中的电子态呈现与横截面势垒分布相同的对称性；电子和空穴沿径向势垒的透射系数和隧穿电流可通过调整势垒高度、以及纳米线截面内的空间分布等进行调制；棱柱型截面纳米线较圆柱型纳米线各向异性较强，将会在隧穿电流-电压曲线内引入更多的电流峰，从而使利用电压调节隧穿电流变得困难，这将使以隧穿为主要工作机制的器件性能因多峰噪声而性能变差. 研究双势垒核壳结构纳米线中的载流子共振隧穿现象以及隧穿电流-电压特性曲线，结合深紫外发光二极管中设计要求，发现双势垒结构电子阻挡层可通过调节势垒参数可在有效阻止电子溢出的同时使得空穴可以隧穿形式注入至有源区，从而提升内量子效率. 研究成果解释和预言了异质结构纳米线中隧穿的物理机制，期待为半导体纳米线器件中载流子隧穿相关的性能优化提供理论依据.