Mendis B G
Department of Physics, Durham University, Durham, DH1 3LE, UK.
Ultramicroscopy. 2019 Sep;204:73-80. doi: 10.1016/j.ultramic.2019.05.007. Epub 2019 May 20.
Cathodoluminescence (CL) is an important analytical technique for probing the optical properties of materials at high spatial resolution. Interpretation of CL spectra is however complicated by the fact that the spectrum depends on the carrier injection density of the incident electron beam. Here a generalised version of Planck's radiation law is used to uncover the evolution of CL spectra with injection under steady-state conditions. The importance of the quasi-Fermi level is highlighted and it is shown that steady-state luminescence is suppressed when the carrier distributions undergo a population inversion. The theory is consistent with some well-known luminescence phenomena, such as the blue shifting of donor-acceptor pair transitions with increased injection, and its predictions are experimentally verified on CdTe and GaN, which are exemplar thin-film solar cell and light emitting diode materials respectively. Furthermore, the discussion is broadened to include pulsed illumination in time resolved CL, where the carrier distribution is dynamically evolving with time.
阴极发光（CL）是一种重要的分析技术，用于在高空间分辨率下探测材料的光学特性。然而，由于光谱取决于入射电子束的载流子注入密度，CL光谱的解释变得复杂。在此，普朗克辐射定律的广义版本被用于揭示稳态条件下注入时CL光谱的演变。准费米能级的重要性得到了强调，结果表明，当载流子分布发生粒子数反转时，稳态发光会受到抑制。该理论与一些著名的发光现象一致，例如随着注入增加，施主-受主对跃迁的蓝移，并且其预测在CdTe和GaN上得到了实验验证，CdTe和GaN分别是典型的薄膜太阳能电池和发光二极管材料。此外，讨论范围扩大到包括时间分辨CL中的脉冲照明，其中载流子分布随时间动态演变。
