半导体纳米颗粒载流子的超快弛豫过程

Ultrafast relaxation process of photoexcited charge carriers in semiconductor nanoparticles

分析了纳米颗粒的能级结构,建立了载流子弛豫的简化模型,运用数值模拟方法讨论了激发密度、表面态密度及俘获态电子的弛豫率对弛豫过程的影响。讨论结果表明,激发密度的增大及表面态的减少都会导致表面态上电子的饱和,使导带上出现电子的积累,导带电子寿命增大;深俘获态电子的弛豫是影响材料响应速度的主要因素。应用此模型对近红外泵浦探测实验的结果进行分析,表明模型可望在实验结果分析上得到应用。

Ultrafast relaxation process of photoexcited charge carriers in semiconductor nanoparticles is modeled with the analysis of state levels structure. Several parameters, that affect this process, are discussed. The result shows that, with the increasing of excited intensity or decreasing of surface state density, the electron saturation of the surface state would cause the electron build-up of conduction state and lead to a longer life time. The relaxation of deep trapped electrons is the main limit of response time for nanoparticles. The model is used to analyze pump-probe experiment, showing potential use in experimental analysis.