Zhang Bowen, Nie Zhaogang, Wang Bo, Wang Dengkui, Tang Jilong, Wang Xiaohua, Zhang Jiahua, Xing Guichuan, Zhang Wenchun, Wei Zhipeng
State Key Laboratory of High-Power Semiconductor Laser, School of Science, Changchun University of Science and Technology, 7089 Wei-Xing Road, Changchun 130022, China.
Phys Chem Chem Phys. 2020 Nov 18;22(44):25819-25826. doi: 10.1039/d0cp04250a.
Femtosecond optical pump-probe spectroscopy is employed to elucidate the ultrafast carrier nonradiative relaxation dynamics of bare GaAs and a core-shell GaAs/AlGaAs semiconductor nanowire array. Different from the single nanowire conventionally used for the study of ultrafast dynamics, a simple spin coating and peeling off method was performed to prepare transparent organic films containing a vertical oriented nanowire array for transient absorption measurement. The transient experiment provides the direct observation of carrier thermalization, carrier cooling, thermal dissipation and band-gap energy evolutions along with the carrier relaxations. Carrier thermalization occurs within sub-0.5 ps and proceeds almost independently on the AlGaAs-coating, while the time constants of carrier cooling and thermal dissipation are increased by an order of magnitude due to the AlGaAs-coating effect. The concomitant band-gap evolutions in GaAs and GaAs/AlGaAs include an initial rapid red-shift in thermalization period, followed by a slow blue and/or red shift in carrier cooling, and then by an even slower blue shift in thermal dissipation. The evolution is explained by the competition of band-gap renormalization, plasma screening and band-filling. These findings are significant for understanding the basic physics of carrier scattering, and also for the development of flexible optoelectronic devices.
飞秒光泵浦-探测光谱法被用于阐明裸GaAs以及核壳结构GaAs/AlGaAs半导体纳米线阵列的超快载流子非辐射弛豫动力学。与传统用于超快动力学研究的单根纳米线不同，采用了一种简单的旋涂和剥离方法来制备包含垂直取向纳米线阵列的透明有机薄膜，用于瞬态吸收测量。瞬态实验直接观察了载流子热化、载流子冷却、热耗散以及带隙能量随载流子弛豫的演化。载流子热化在亚0.5皮秒内发生，并且几乎不受AlGaAs涂层的影响独立进行，而由于AlGaAs涂层效应，载流子冷却和热耗散的时间常数增加了一个数量级。GaAs和GaAs/AlGaAs中伴随的带隙演化包括热化阶段初始的快速红移，随后在载流子冷却阶段有缓慢的蓝移和/或红移，然后在热耗散阶段有更缓慢的蓝移。这种演化可以通过带隙重整化、等离子体屏蔽和能带填充的竞争来解释。这些发现对于理解载流子散射的基本物理原理具有重要意义，同时也对柔性光电器件的发展具有重要意义。
