Fundamental Properties of GaAsN and InGaAsN - Toward Optoelectronic Applications

提出了在GaAs衬底上生长和表征常规III-V化合物(如GaN、InAs)和III-N化合物(如GaN、InN)的三元合金。这些合金应该是立方体的闪锌矿结构，并且没有直接的带隙。然而，由于GaAs和GaN之间的晶格失配很大，以及As和N之间的原子轨道能量的差异，导致了禁带的成分依赖关系。GaAs1-xNx的光学弯曲系数至少比常见的III-V合金的光学弯曲系数大一个数量级。其禁带宽度随N含量的增加而迅速减小。这为在1.3-1.55 mm的GaAs衬底上制备新型光电子器件提供了可能。本研究所需要的材料将用金属有机分子束外延(MOMBE)生长。氮掺杂对外延层的物理微结构和光学带隙的影响将由各种实验技术来确定。拉曼散射将被用来研究微结构效应，如氮掺杂、自发有序和相分离。拉曼结果将被用键极化率、两组分分子模型、有限尺寸和应变效应来模拟。近带边光学性质将用连续波和时间分辨光致发光进行深入的研究。这些将集中在氮掺入如何改变载体重组。用椭偏法和反射法获得上述禁带光学性质的信息，用现象形变势模型考虑InGaAsN/GaAs的量子阱和超晶格中的应变效应。最后，基于InGaAsN/GaAs的量子阱结构将被用作有源层，以制作工作在1.3-1.55 mm波长范围内的垂直腔激光器。

It is proposed to grow and characterize ternary alloys of conventional III-Vcompounds (e.g. GaAs, InAs) with III-N compounds (e.g. GaN, InN) on GaAssubstrates. These alloys are expected to be cubic with the zincblende structure and topossess a direct bandgap. However, the large lattice mismatch between GaAs and GaNand the difference in atomic orbital energies between As and N result in a very unusualcompositional dependence of the bandgap. The optical bowing coefficients in GaAs1-xNxare at least an order of magnitude greater than those encountered in common III-Valloys. Its bandgap decreases rapidly with increasing N fraction. This offers a possibilityof preparing novel optoelectronic devices, on GaAs substrates, operating in the 1.3 - 1.55mm range. The materials needed for this study will be grown by Metalorganic MolecularBeam Epitaxy (MOMBE). The effect of nitrogen incorporation on physicalmicrostructure and optical bandgap of epitaxial layers will be determined by a variety ofexperimental techniques. Raman scattering will be used to investigate microstructuraleffects such as nitrogen incorporation, spontaneous ordering, and phase separation.Raman results will be modeled using bond polarizability, a two-component molecularmodel, finite size, and strain effects. Near band edge optical properties will be studiedextensively by cw and time-resolved photoluminescence. These will focus on hownitrogen incorporation modifies carrier recombination. Ellipsometry and reflectancemethods will be used to gain information of the above-bandgap optical properties.Phenomenological deformation potentials model will be used to account for strain effectsin quantum wells and superlattices of InGaAsN/GaAs. Finally, quantum well structuresbased on InGaAsN/GaAs will be used as active layers to make vertical cavity lasersoperating in the wavelength range of 1.3-1.55 mm.