GaAs/AlGaAs量子阱中飞秒超快光谱研究

Transient Femtosecond Spectroscopy in GaAs/AlGaAs Multiquantum Wells

使用飞秒白光泵浦探测技术研究了GaAs/AlGaAs量子阱材料中超快动力学行为。采用了非共振泵浦,激发了不满足Δn=2p选择定则的光跃迁,观察到差分透射谱中的3个吸收跃迁饱和漂白峰。一方面,E1导带上的电子和HH2上的空穴通过各种散射和复合而快速减少,E1-HH2和E2-HH2峰迅速衰减;另一方面,由于处在带边的复杂性致使E1-HH1峰在25ps内几乎没有衰减。与掺杂多量阱材料的驰豫动力学比较可知,超晶格中由于阱间波函数的耦合使载流子的散射加快;而掺杂多量子阱中由于捕获中心的存在使载流子的复合加快。

Ultrafast dynamic process in GaAs/AlGaAs quantum wells was studied by femtosecond white light pump-probe technique.Three distinct bleaching peaks in differential transmission spectrum were observed by the E 1-HH 1,E 1-HH 2 and E 2-HH 2 transitions.The pumped transition in GaAs/AlGaAs thin film was excited unresonantly by the strong laser,which cannot be well explained by the selection rules of Δn=2p.The peaks of the E 1-HH 2 and the E 2-HH 2 fall quickly because the electrons on the conduction band of E_1 and the holes on the valence band of HH 2 decrease quickly through the processes of the scatterings and recombination.However,the peak of E 1-HH 1 nearly does not change in the 25 ps because it is at the edge of the band gap.Comparing with the doped multiquantum wells,the scattering in the superlattice is faster because of the coupling of the wave functions in wells.The recombination in the doped multiquantum wells is faster than that in the superlattice because of the existence of the capture center in the doped multiquantum wells.