Ultrafast imaging of surface-exclusive carrier dynamics in silicon
Ultrafast imaging of surface-exclusive carrier dynamics in silicon
复制标题
硅中表面专有载流子动力学的超快成像
DOI：
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发表时间：
2019
影响因子：
3.2
通讯作者：
Amir Jafari
中科院分区：
文献类型：
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作者：
E. Najafi;Amir Jafari
了解在半导体表面和界面的载流子的动力学是光催化，光伏和光电器件的进一步发展的基础。在这里，我们使用扫描超快电子显微镜（SUEM）研究本征和掺杂硅的表面光电压（SPV）动力学。SUEM是一种表面敏感技术，允许在超快时间尺度上直接成像的载流子，从而阐明他们的时空响应光激发。我们首先讨论了在SUEM图像形成的机制。然后，我们使用这些图像显示，硅表面上的载流子动力学强烈依赖于掺杂类型和浓度，虽然并不总是由SPV决定。漂移扩散模型的数值模拟表明，这是由于形成复杂的运输过程，驱动的激发体积中的本征和光致场。这项工作完善了我们目前对半导体表面排他动力学的理解，引入了一种方法来研究它们在空间和时间上的演化，并提供了一个模型来解释潜在的机制。
Understanding the dynamics of charge carriers at the semiconductor surfaces and interfaces is fundamental to the further development of photocatalytic, photovoltaic, and optoelectronic devices. Here, we study the surface photovoltage (SPV) dynamics in intrinsic and doped silicon using scanning ultrafast electron microscopy (SUEM). SUEM is a surface sensitive technique that allows the direct imaging of carriers at ultrafast time scales, thereby elucidating their spatiotemporal response to optical excitation. We first discuss the mechanism of image formation in SUEM. We then use these images to show that carrier dynamics on the silicon surface depends strongly on the doping type and concentration, though not always dictated by SPV. The numerical simulation of the drift-diffusion model suggests that this is due to the formation of complex transport processes, driven by intrinsic and photoinduced fields in the excited volume. This work refines our current understanding of the surface-exclusive dynamics in semiconductors by introducing a means to study their evolution in space and time and providing a model to explain the underlying mechanism.