GaAs/AlAs超晶格的近共振喇曼散射研究

NEAR RESONANT RAMAN SCATTERING FROM GaAs/AlAs SUPERLATTICES

本文介绍GaAs/AlAs超晶格的室温近共振喇曼散射测量结果。由于超晶格中Frhlich相互作用的共振增强效应,GaAs LO声子偶模的散射得到了很大的增强。和前人的结果一样,在偏振谱我们观察到了偶模。但和前人的结果不同,在退偏振谱中我们观察到的是奇模,而不是偶模。从而证明了在近共振条件下LO声子限制模仍遵从与非共振时一样的选择定则。二级喇曼散射实验结果表明,在偏振谱中二级谱是由两个偶模组合而成,而在退偏振谱中的二级谱与前人的结果不同,由一个奇模与一个偶模组合而成。上述结果与最近提出的黄朱模型的预言是一致的。还简单讨论了所观察到的界面模及其与限制模的组合谱。

This article presents the results of near resonant Raman scattering measurement of GaAs/ AlAs superlattices at room temperature. A strong enhancement of GaAs LO phonon even modes resulted owing to dipole allowed Frohlich interaction in superlattices. Similar to the previous results, the LO phonon even modes in polarized configuration is observed. In contrast to the previous works, however, what we observed in depolarized configuration is the LO phonon odd modes instead of even modes. And it is confirmed that the selection rules of near resonant Raman scattering from LO phonons in this kind of superlattices is the same as that of off resonant scattering. From the second-order Raman scattering, it is confirmed that polarized second-order Raman scattering spectra consist of overtone and combinations of two even modes and depolarized second-order Raman scattering spectra consist of combinations of an even mode and an odd mode. Our experimental results coincide with the predictions using recently developed Huang-Zhu model. A brief discussion on interface modes and their combination with confined modes are also presented.