EXCITONIC AND NONLINEAR-OPTICAL PROPERTIES OF DIELECTRIC QUANTUM-WELL STRUCTURES
EXCITONIC AND NONLINEAR-OPTICAL PROPERTIES OF DIELECTRIC QUANTUM-WELL STRUCTURES
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DOI：
10.1103/physrevb.40.12359
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发表时间：
1989-12-15
影响因子：
3.7
通讯作者：
TAKAGAHARA, T
中科院分区：
文献类型：
--
作者：
KUMAGAI, M;TAKAGAHARA, T
从理论上研究了介质量子阱(DQW)结构的激子和非线性光学特性。DQW是一种夹有介电常数较小、带隙较大的势垒材料的量子阱。阐明了决定DQW中激子性质的基本物理性质，即激子结合能、激子振子强度和非线性光学响应。提高激子性质最重要的机制是量子限制效应、质量限制效应和介电限制效应。由于势垒限制，量子限制增加了电子和空穴之间的空间重叠，从而提高了振子强度。质量约束是基于载波函数对有效质量大于势垒层的势垒层的穿透。它增加了激子的折合质量，从而增加了激子的结合能。介电约束是由于电场穿透到介电常数小于势垒介质的势垒介质而引起的整个系统的有效介电常数的降低，并增强了电子与空穴之间的库仑相互作用。在这些分析的基础上，建立了设计具有最佳激子性能的DQW结构的一般指导原则。从晶格常数匹配、介电常数的差异、载流子有效质量的差异等方面考察了DQW的各种应用实例。锌硒被认为是最有前途的GaAsDQW势垒材料之一。
Excitonic and nonlinear-optical properties of dielectric quantum-well (DQW) structures are investigated theoretically. A DQW is a quantum well sandwiched by barrier materials with a smaller dielectric constant and a larger band gap than the well material. The fundamental physics determining the excitonic properties in a DQW, ie, exciton binding energy, exciton oscillator strength, and nonlinear-optical response, are clarified. The most important mechanisms for enhancing the excitonic properties are quantum-confinement effect, mass-confinement effect, and dielectric-confinement effect. Quantum confinement increases the spatial overlap between an electron and a hole as a result of the potential well confinement, and it enhances oscillator strength. Mass confinement is based on the penetration of the carrier wave function into barrier layers with a heavier effective mass than the well layer. It increases the exciton reduced mass and hence the exciton binding energy. Dielectric confinement arises from the reduction of the effective dielectric constant of the whole system due to the penetration of the electric field into the barrier medium having a smaller dielectric constant than the well and enhances the Coulomb interaction between the electron and hole. On the basis of these analyses, the general guiding principles are established for designing DQW structures with optimum excitonic properties. Various practical examples of DQW's are examined with respect to the lattice-constant matching, the difference in the dielectric constant, and the difference in the carrier effective masses. ZnSe is found to be one of the most promising candidates for the barrier material of the GaAs DQW.