II-VI族半导体多层异质结构中电-声子相互作用及相关问题

Semiconductor heterostructures are the basic units to construct electronic and optoelectronic devices. In recent years, researches on the physical properties of II-VI group semiconductor ZnO with wide forbidden band and low price, component modulated ternary mixed crystals (TMCs) MgxZn1-xO and related heterostructures MgxZn1-xO/ZnO have been showing that this kind of heterostructures, quantum wells and multilayered structures has prosperous and wide applications in ultraviolet/blue short wave light emitters, quantum spin transport devices, lasers, and high electronic mobility transistors, etc. to attract much interest of researchers exploring the related theories and experiments. . Based on continuous medium model in this project, the characteristics, dispersion relations, phonon potentials of different kinds of optical phonon modes in multilayered heterostructure materials (mainly focusing on MgxZn1-x O/ZnO) consisting of II-VI group ternary mixed crystal (TMC) semiconductors are discussed in consideration of the change of physical constants such as dielectric constants, energy band offset and electronic (hole) effective mass, etc. varying with components and size of the TMCs. The existing conditions of different kinds of phonon modes, the critical transition components between them, and the Hamiltonians of interaction between electrons and phonons are obtained. On the basis of discussing the electron (hole) states, exciton states, the influence on the light absorption due to the electron (hole) subband transition and exciton transition in these systems and the influences from TMC effect and size effect, the polaronic effect from the different kinds of phonons on the transitions are investigated. The scattering on the current carriers parallel to the interface direction from different kinds of optical phonons are investigated to discuss TMC effect and size effect enhancing the transport property of current carriers. The effects of electric fields including the built-in electric field induced by spontaneous and piezoelectric polarizations and external fields are discussed to understand their influences on light absorption due to the transition of electrons, holes, and excitons, as well as the transport of current carriers. Our project will play theoretical guidance to explain and predict novel experimental phenomena, to optimize the structures and characteristics of electronic, optoelectronic materials and devices.

本项目基于连续介质模型，考虑界面晶格失配引起的应变调制作用，计入材料的介电函数、能带错位及电子（空穴）有效质量等物理参数随三元混晶（TMC）组分和尺寸的变化，讨论II-VI族TMC多层异质结构材料（重点为MgxZn1-xO/ZnO）中各类光学声子模式的特征、色散关系、声子势，获得各类声子模存在条件和转变的临界组分及电-声子相互作用哈密顿。在探讨系统中电子（空穴）态、激子态、电子（空穴）子带跃迁和激子跃迁对光吸收的影响及TMC和尺寸效应的基础上，讨论各类光学声子对上述电子（空穴）态和激子态跃迁影响的极化子效应。研究各类光学声子对载流子平行界面方向的散射，讨论TMC效应和尺寸效应对提高载流子输运性质的作用。理解由自发极化和压电极化效应导致的强内建电场和外电场对电子和空穴跃迁及激子跃迁光吸收、载流子输运的作用。对解释和预言实验现象、优化电子、光电子材料和器件结构和特性发挥理论指导作用。

半导体异质结构是构成电子、光电子器件的基本单元，近年来对宽禁带和低价位II-VI族半导体ZnO、组分调制三元混晶MgxZn1-xO、以及半导体异质结构MgxZn1-xO/ZnO等材料的探索已显示：此类异质结构、量子阱和多层结构已在远紫外/蓝短波光发射器、量子自旋输运器件、激光器和高电子迁移率晶体管等展现出诱人的应用前景，从而吸引了人们对相关理论和实验探索的极大兴趣。.本项目基于连续介质模型，考虑界面晶格失配引起的应变调制作用，计入材料的介电函数、能带错位及电子（空穴）有效质量等物理参数随三元混晶组分和尺寸的变化，讨论II-VI族三元混晶多层异质结构材料（重点为MgxZn1-xO/ZnO）及性质相近系统中各类光学声子模式的特征、色散关系、声子势，获得各类声子模存在条件和转变的临界组分及电-声子相互作用哈密顿。在探讨系统中电子（空穴）态、激子态、电子（空穴）子带跃迁和激子跃迁对光吸收的影响及三元混晶和尺寸效应的基础上，讨论各类光学声子对上述电子（空穴）态和激子态跃迁影响的极化子效应。研究各类光学声子对载流子平行界面方向的散射，给出三元混晶效应和尺寸效应对提高载流子输运性质的定量结果。理解由自发极化和压电极化效应导致的强内建电场和外电场对电子和空穴跃迁及激子跃迁光吸收、载流子输运的调制作用。针对在0.37<x<0.62范围内纤锌矿与闪锌矿的混相多层异质结构，我们提出了权重模型，讨论体系的上述物性。本项目不仅对解释和预言实验现象、优化电子、光电子材料和器件结构和特性发挥了理论指导作用，而且对推动相关理论发展起到了积极作用。