Dynamics of high-density excitons and electron hole plasma in ZnO epitaxial thin films
Dynamics of high-density excitons and electron hole plasma in ZnO epitaxial thin films
复制标题
DOI：
10.1016/j.jlumin.2006.01.003
复制
发表时间：
2006-07
影响因子：
3.6
通讯作者：
Nobuyuki Araia;Jun Takedaa;Hang-Ju Kob;T. Yaob
中科院分区：
文献类型：
--
作者：
Nobuyuki Araia;Jun Takedaa;Hang-Ju Kob;T. Yaob
通过光学克尔门方法，在带间激发下，测量了 ZnO 外延薄膜中电子空穴等离子体（EHP 发射）和激子-激子散射过程（P 发射）引起的时间分辨发光光谱。我们发现 EHP 和 P 排放都出现了几皮秒的长时间延迟。观察到的时间延迟随着激发密度低于临界莫特密度而呈二次方减少。这些结果意味着，通过多个LO声子发射完成激子（电子和空穴）向激子带底（重整化带隙）的热冷却后，出现P（EHP）发射。随着激发密度的增加，激子-激子散射过程对高密度激子的冷却和弛豫也起着重要作用。
Time-resolved luminescence spectra due to an electron–hole plasma (EHP emission) and an exciton–exciton scattering process (P emission) were measured in ZnO epitaxial thin films under band-to-band excitation by the optical Kerr gate method. We find that both the EHP and P emissions emerge with a long time delay of a few picoseconds. The time delay observed decreases quadratically with the excitation density below the critical Mott density. These results imply that the P (EHP) emission emerges after completing thermal cooling of excitons (electrons and holes) toward the exciton band bottom (renormalized band gap) through multiple LO-phonon emissions. As the excitation density increases, the exciton–exciton scattering process also plays an important role on cooling and relaxation of high-density excitons.