School of Physics and Electronic Engineering, Guangzhou University, Guangzhou 510006, China.
Solid State Physics and NanoLund, Lund University, Lund 22100, Sweden.
Nanoscale. 2019 Oct 28;11(40):18550-18558. doi: 10.1039/c9nr03187a. Epub 2019 Jul 31.
Introduction of in situ HCl etching to an epitaxial growth process has been shown to suppress radial growth and improve the morphology and optical properties of nanowires. In this paper, we investigate the dynamics of photo-generated charge carriers in a series of indium phosphide nanowires grown with varied HCl fluxes. Time resolved photo-induced luminescence, transient absorption and time resolved terahertz spectroscopy were employed to investigate charge trapping and recombination processes in the nanowires. Since the excitation photons generate charges predominantly in less than a half length of the nanowires, we can selectively assess the charge carrier dynamics at their top and bottom. We found that the photoluminescence decay is dominated by the decay of the mobile hole population due to trapping, which is affected by the HCl etching. The hole trapping rate is in general faster at the top of the nanowires than at the bottom. In contrast, electrons remain highly mobile until they recombine non-radiatively with the trapped holes. The slowest hole trapping as well as the least efficient non-radiative recombination was recorded for etching using the HCl molar fraction of χ = 5.4 × 10.
在外延生长过程中引入原位 HCl 刻蚀已被证明可以抑制径向生长，改善纳米线的形貌和光学性能。在本文中，我们研究了在不同 HCl 流量下生长的一系列磷化铟纳米线中光生电荷载流子的动力学。我们采用时间分辨光致发光、瞬态吸收和时间分辨太赫兹光谱来研究纳米线中的电荷俘获和复合过程。由于激发光子主要在不到纳米线一半长度的范围内产生电荷，我们可以选择性地评估纳米线顶部和底部的载流子动力学。我们发现，光致发光衰减主要由由于俘获而导致的可移动空穴群体的衰减主导，这受到 HCl 刻蚀的影响。空穴俘获速率通常在纳米线的顶部比在底部更快。相比之下，电子在与俘获的空穴非辐射复合之前保持高度移动。对于使用 HCl 摩尔分数 χ = 5.4×10 的刻蚀，记录到最慢的空穴俘获以及最低效的非辐射复合。
