Zhang Yaqing, Chen Xiang, Yu Yaocheng, Huang Yue, Qiu Moxi, Liu Fang, Feng Min, Gao Cuntao, Deng Shibing, Fu Xuewen
Ultrafast Electron Microscopy Laboratory, MOE Key Laboratory of Weak-Light Nonlinear Photonics, School of Physics, Nankai University, Tianjin, 300071, China.
School of Materials Science and Engineering, Smart Sensing Interdisciplinary Science Center, Nankai University, Tianjin, 300350, China.
Adv Sci (Weinh). 2024 Aug;11(31):e2400633. doi: 10.1002/advs.202400633. Epub 2024 Jun 18.
Carrier dynamics detection in different dimensions (space, time, and energy) with high resolutions plays a pivotal role in the development of modern semiconductor devices, especially in low-dimensional, high-speed, and ultrasensitive devices. Here, a femtosecond electron-based versatile microscopy is reported that combines scanning ultrafast electron microscopy (SUEM) imaging and time-resolved cathodoluminescence (TRCL) detection, which allows for visualizing and decoupling different dynamic processes of carriers involved in surface and bulk in semiconductors with unprecedented spatiotemporal and energetic resolutions. The achieved spatial resolution is better than 10 nm, and the temporal resolutions for SUEM imaging and TRCL detection are ≈500 fs and ≈4.5 ps, respectively, representing state-of-the-art performance. To demonstrate its unique capability, the surface and bulk carrier dynamics involved in n-type gallium arsenide (GaAs) are directly tracked and distinguished. It is revealed, in real time and space, that hot carrier cooling, defect trapping, and interband-/defect-assisted radiative recombination in the energy domain result in ordinal super-diffusion, localization, and sub-diffusion of carriers at the surface, elucidating the crucial role of surface states on carrier dynamics. The study not only gives a comprehensive physical picture of carrier dynamics in GaAs, but also provides a powerful platform for exploring complex carrier dynamics in semiconductors for promoting their device performance.
在不同维度（空间、时间和能量）上进行高分辨率的载流子动力学检测，在现代半导体器件的发展中起着关键作用，特别是在低维、高速和超灵敏器件中。在此，报道了一种基于飞秒电子的多功能显微镜，它结合了扫描超快电子显微镜（SUEM）成像和时间分辨阴极发光（TRCL）检测，能够以前所未有的时空和能量分辨率可视化并解耦半导体表面和体内载流子的不同动态过程。实现的空间分辨率优于10纳米，SUEM成像和TRCL检测的时间分辨率分别约为500飞秒和约4.5皮秒，代表了当前的先进性能。为了展示其独特能力，直接跟踪并区分了n型砷化镓（GaAs）中涉及的表面和体内载流子动力学。实时、空间分辨地揭示了能量域中的热载流子冷却、缺陷俘获以及带间/缺陷辅助辐射复合导致表面载流子依次发生超扩散、局域化和亚扩散，阐明了表面态对载流子动力学的关键作用。该研究不仅给出了GaAs中载流子动力学的全面物理图像，还为探索半导体中的复杂载流子动力学以提升其器件性能提供了一个强大的平台。
