Lattice Dynamics of Thin-layered Semiconductor Superlattices

1.导论最近薄膜生长技术的进步使我们能够制造出新的人造半导体超晶格。从晶格动力学的角度，拉曼散射实验揭示了光学声子限制、声色散的区域折叠效应以及界面模的存在等新的性质。在目前的研究方案中，我们通过计算拉曼光谱来探索超晶格和薄表面层中的纵向光学(LO)声子。我们还通过电子-声子相互作用研究了声子对二维电子性质的影响。结果和讨论我们用LO声子在GaAsAlxGa1-x&gt；As超晶格中拉曼光谱的结果很好地描述了观测到的拉曼分布。与受限LO声子相关的拉曼强度与构成超晶格的层的厚度有关。讨论了声子衰减对拉曼谱的重要影响，并考虑了合金AlGaAs层中的势能起伏引起的衰减增加。对P型GaAs拉曼光谱的分析也揭示了表面LO声子对整个光谱的贡献。

1. IntroductionRecent advance of thin-film growth techniques has enable us to fabricate new man-made semiconductor superlattices. From lattice dynamical aspects, raman scattering experiments have revealed new properties, such as optical phonon confinement, zone-folding effects on the acoustic dispersion, and existence of the interface modes. In the present research program, we explore the longitudinal optical (lo) phonons in superlattices and thin surface layer by calculating the raman spectra. We also study the two-dimensional electronic properties which are affected much by phonons via electron-phonon interactions.2. Results and DiscussionsOur results for the Raman spectra by the LO phonons in GaAs-AL_xGa_<1-x>As superlattices provide a good description of the observed raman profile. The raman intensity associated with the confined lo phonons are related with the thickness of layers which constitute the superlattices. The important effects of phonon damping on raman spectra are discussed by taging into account the increase of damping due to potential fluctuations in alloy AlGaAs layer. Analysis of Raman spectra from P-type GaAs have also revealed the contribution from the surface LO phonons to whole spectra.