【作者】 哈斯花；

【导师】 班士良；

【作者基本信息】 内蒙古大学 ， 理论物理， 2008， 博士

【摘要】 近十年来,诸如AIN、GaN和InN等闪锌矿和纤锌矿Ⅲ-族氮化物半导体材料在发光二极管和激光二极管等器件制备方面的应用日益丰富,其低维结构的研究成为理论界的热点问题之一.尤其值得注意的是,氮化物半导体的不同晶格结构及不同轴向的选取,以及出现在量子阱界面处由晶格失配引起的极化电荷及由此引起的强内建电场,这些都将影响量子阱中激子的行为.另外,鉴于流体静压力对材料物性的调制作用,应变氮化物量子阱中受屏蔽激子的压力效应的研究变得更加有意义.本文首先求解受电子-空穴气屏蔽的有限深量子阱中电子与空穴的本征方程得出其本征函数及相应的本征值.之后,在单带模型和有效质量近似下,结合变分法和自洽计算方法,讨论闪锌矿及纤锌矿GaN/Al_xGa_1-xN量子阱中激子的结合能.其中,考虑到流体静压力和电子-空穴气体屏蔽的影响,分别计算纤锌矿（[0001]取向）和闪锌矿（[001]和[111]取向）GaN/Al_xGa_1-xN量子阱中激子的结合能.最后,计入电子（空穴）与局域体纵光学声子和界面光学声子相互作用,计算纤锌矿应变量子阱中受屏蔽激子的结合能并讨论其压力效应.对于电子和空穴的本征方程,则采用自洽计算泊松方程和薛定谔方程的方法数值求解.结果表明,一方面,内建电场使电子和空穴分离并分别向两边势垒运动;另一方面,电子-空穴气体将屏蔽内建电场,使得电子和空穴向阱中心移动.对于闪锌矿或纤锌矿量子阱中激子的计算结果表明,即使考虑压力对应变的调制,其结合能随压力的增加仍然近似线性增加.而且,由于压力对屏蔽效应和排斥作用的影响,结合能增加的百分比还会依赖电子-空穴气体密度而变化.计及光学声子与激子的相互作用,计算纤锌矿应变量子阱中受屏蔽激子的结合能之结果表明声子对结合能的贡献为负值,且随电子-空穴气密度的增加,先缓慢增加到一个极大值随后迅速降低为零.激子会在某一个极大的电子-空穴气密度值坍塌分离为自由的电子和空穴,此时声子的贡献也降为零.并且,局域和界面光学声子对结合能的单独贡献随压力的增加呈线性增加,增加的百分比随电子-空穴气密度的增加而降低.更多还原

【Abstract】 In recent decades,the low-dimensional structures made of wurtzite and zinc-blende group-Ⅲnitride semiconductors such as A1N,GaN and InN were paid much attention owing to their promising application in light-emitting diodes,laser diodes and so on.In particular,different lattice structures,different grown axes,the polarized charges induced by lattice mismatch present at the interface and the strong built-in electric field induced by the charges consequentially influence the properties of excitons in strained nitride quantum wells（QWs）.Furthennore,the investigation of pressure effect on the screened excitons in strained nitride QWs becomes more significant due to the modulation to the physical properties of materials by pressure.In this thesis,the eigenequations for electrons and holes in QWs with finite barriers under the influence of screening effect induced by the electron-hole gas are solved firstly to obtain the eigenfunctions and their corresponding eigenvalues.Then, in the framework of effective mass and single-band approximation,a variational method combined with a self-consistent procedure is adopted to discuss the binding energies of excitons in strained wurtzite and zinc-blende GaN/Al_xGa_1-xN QWs.By considering the hydrostatic pressure effect and screening due to the electron-hole gas, the binding energies of excitons in wurtzite（[0001J-oriented） and zinc-blende（[001]-and [111]-oriented） GaN/A1_xGa_1-xN QWs are investigated,respectively.Finally,the interaction between electrons（holes） and confined bulk longitudinal optical phonons and interface optical phonons is considered to calculate the binding energies of screened excitons in wurtzite strained QWs,and the pressure effect is also discussed.For the eigenequations of electrons and holes,the numerical results are computed by solving self-consistently the Poisson equation and Schrodinger equation. The result shows that the built-in electric field separates electrons and holes to move towards the opposite barriers respectively,whereas the presence of the electron-hole gas will screen the field and inforce electrons and holes to move towards the center of the wells.Furthermore,the results about excitons in wurtzite or zinc-blende strained QWs indicate that the binding energies nearly linearly increase with pressure even under consideration of the modulation to strain by pressure.It is also found that the increase percentage of the binding energy with pressure is influenced by the electron-hole density due to the pressure influence on the screening and exclusion effects.Under consideration of the interaction between excitons and optical phonons, the results show that the negative contribution from phonons to the binding energy increases first,then reaches a maximum and decreases finally as the electron-hole density increases.The phononic contribution decreases to be zero at some large electron-hole density where the exciton collapses,It is also found that the contributions from confined and interface optical phonons to the binding energies of excitons linearly increase with pressure and the increase percentages are lowered as the electron-hole density increases.更多还原