Evolution of Electron-Hole Plasma and Excitons in ZnO Epitaxial Thin Films Studied by Femtosecond Spectroscopy
Evolution of Electron-Hole Plasma and Excitons in ZnO Epitaxial Thin Films Studied by Femtosecond Spectroscopy
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飞秒光谱研究 ZnO 外延薄膜中电子空穴等离子体和激子的演化
DOI：
10.1080/1058726021000044613
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
T. Yao
中科院分区：
文献类型：
--
作者：
K. Takagi;Y. Toshine;J. Takeda;S. Kurita;Y. Chen;T. Yao
为了阐明光激高密度载流子的动力学特性，利用泵浦-探测吸收和亚皮秒时间分辨的克尔栅光致发光技术，研究了激子态共振激发下高密度电子空穴等离子体(EHP)和激子在氧化锌外延薄膜中的时间演化。激子吸收的漂白没有任何可测量的延迟时间，这表明由于库仑相互作用的屏蔽，高密度激子解离到EHP中，激子态瞬间变得不稳定。这导致了瞬时的带隙减小。由于电子与空穴的辐射复合，随着载流子密度的降低，重整化禁带的恢复和激子漂白也随之发生。通过时间分辨吸收和发光实验，确定其恢复时间为25V ps。
Time evolution of a high density electron-hole plasma (EHP) and excitons in ZnO epitaxial thin films was studied under resonant excitation of the excitonic state using pump-probe absorption and optical Kerr gate luminescence techniques with sub-picosecond time resolution in order to elucidate dynamics of the photo-excited high density carriers. The bleaching of the exciton absorption occurs without any measurable delay time, suggesting that the excitonic state instantaneously becomes unstable because of the dissociation of the high density excitons into the EHP due to the screening of Coulomb interaction. This leads to an instantaneous bandgap reduction. Then the recovery of the renormalized bandgap as well as that of the exciton bleaching takes place with decreasing the carrier density due to radiative recombination of electrons with holes. From the time-resolved absorption and luminescence experiments, the recovery time is determined to be 25 v ps.