Ultrafast screening and carrier dynamics in ZnO: Theory and experiment
Ultrafast screening and carrier dynamics in ZnO: Theory and experiment
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DOI：
10.1103/physrevb.84.035207
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发表时间：
2010-12
影响因子：
3.7
通讯作者：
M. Versteegh;Tim Kuis;H. Stoof;J. I. Dijkhuis
中科院分区：
文献类型：
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作者：
M. Versteegh;Tim Kuis;H. Stoof;J. I. Dijkhuis
在载流子密度高于莫特密度时，库仑屏蔽破坏了激子共振。这与带隙重整化和带填充一起严重影响了光谱。我们已经实验研究了这些影响的超快泵浦-探测反射率测量ZnO单晶在激子共振周围的各种波长，并在一个广泛的载流子密度范围。理论上，我们确定ZnO中的Mott密度在300 K时为1.5\ifmmode\times\else\texttimes\fi {}{10}^{24}$ m${}^{\ensuremath{-}3}$。采用场论方法，推导并求解了Bethe-Salpeter阶梯方程，并计算了与密度相关的反射率和吸收光谱。建立了载流子动力学模型，包含三光子吸收、载流子冷却和表面附近的载流子捕获。基于我们的模型的理论反射率与实验数据之间的协议是极好的。
At carrier densities above the Mott density, Coulomb screening destroys the exciton resonance. This, together with band-gap renormalization and band filling, severely affects the optical spectra. We have experimentally studied these effects by ultrafast pump-probe reflectivity measurements on a ZnO single crystal at various wavelengths around the exciton resonance and in a broad carrier-density range. Theoretically, we determined the Mott density in ZnO to be $1.5\ifmmode\times\else\texttimes\fi{}{10}^{24}$ m${}^{\ensuremath{-}3}$ at 300 K. Taking a field-theoretical approach, we derived and solved the Bethe-Salpeter ladder equation and we computed the density-dependent reflectivity and absorption spectra. A carrier dynamics model has been developed, containing three-photon absorption, carrier cooling, and carrier trapping near the surface. The agreement between the theoretical reflectivity based on our model and the experimental data is excellent.