Four-dimensional imaging of carrier interface dynamics in p-n junctions
Four-dimensional imaging of carrier interface dynamics in p-n junctions
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DOI：
10.1126/science.aaa0217
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发表时间：
2015-01-09
期刊：
影响因子：
56.9
通讯作者：
Zewail, Ahmed
中科院分区：
文献类型：
--
作者：
Najafi, Ebrahim;Scarborough, Timothy D.;Zewail, Ahmed
界面电荷转移的动力学是理解许多过程的基础，包括光转化为化学能。在这里，我们报告成像的电荷载流子的激发，运输和重组在硅的p-n结，其中的接口是很好地定义在纳米尺度上。记录的图像阐明了光激发后载流子密度的时空行为。我们表明，载流子在p-n结中的分离远远超出耗尽层，从广泛接受的漂移扩散模型的预期结果相反，和整个结的载流子密度的本地化发生高达几十纳秒，这取决于激光能量密度。观察揭示了弹道式的运动，我们提供了一个模型，占时空密度本地化的交界处。
The dynamics of charge transfer at interfaces are fundamental to the understanding of many processes, including light conversion to chemical energy. Here, we report imaging of charge carrier excitation, transport, and recombination in a silicon p-n junction, where the interface is well defined on the nanoscale. The recorded images elucidate the spatiotemporal behavior of carrier density after optical excitation. We show that carrier separation in the p-n junction extends far beyond the depletion layer, contrary to the expected results from the widely accepted drift-diffusion model, and that localization of carrier density across the junction takes place for up to tens of nanoseconds, depending on the laser fluence. The observations reveal a ballistic-type motion, and we provide a model that accounts for the spatiotemporal density localization across the junction.