Santamaria Luigi, Maddalena Pasqualino, Lettieri Stefano
Italian Space Agency (ASI), Space Geodesy Center "G. Colombo", 75100 Matera, Italy.
Dipartimento di Fisica "E. Pancini", Università degli Studi di Napoli "Federico II", Complesso Universitario di Monte S. Angelo, Via Cupa Cintia 21, 80126 Napoli, Italy.
Materials (Basel). 2022 Feb 17;15(4):1515. doi: 10.3390/ma15041515.
Time-resolved photoluminescence (TRPL) analysis is often performed to assess the qualitative features of semiconductor crystals using predetermined functions (e.g., double- or multi-exponentials) to fit the decays of PL intensity. However, in many cases-including the notable case of interband PL in direct gap semiconductors-this approach just provides phenomenological parameters and not fundamental physical quantities. In the present work, we highlight that within a properly chosen range of laser excitation, the TRPL of zinc oxide (ZnO) bulk crystals can be described with excellent precision with second-order kinetics for the total recombination rate. We show that this allows us to define an original method for data analysis, based on evaluating the "instantaneous" recombination rate that drives the initial slope of the decay curves, acquired as a function of the excitation laser fluence. The method is used to fit experimental data, determining useful information on fundamental quantities that appear in the second-order recombination rate, namely the PL (unimolecular) lifetime, the bimolecular recombination coefficient, the non-radiative lifetime and the equilibrium free-carrier concentration. Results reasonably close to those typically obtained in direct gap semiconductors are extracted. The method may represent a useful tool for gaining insight into the recombination processes of a charge carrier in ZnO, and for obtaining quantitative information on ZnO excitonic dynamics.
时间分辨光致发光（TRPL）分析通常用于评估半导体晶体的定性特征，通过使用预定函数（例如双指数或多指数函数）来拟合光致发光强度的衰减。然而，在许多情况下，包括直接带隙半导体中的带间光致发光这种显著情况，这种方法仅提供现象学参数，而非基本物理量。在本工作中，我们强调在适当选择的激光激发范围内，氧化锌（ZnO）体晶体的TRPL可以用总复合率的二级动力学以极高的精度进行描述。我们表明，这使我们能够基于评估驱动衰减曲线初始斜率的“瞬时”复合率来定义一种原始的数据分析方法，该衰减曲线是作为激发激光能量密度的函数获取的。该方法用于拟合实验数据，确定出现在二级复合率中的基本量的有用信息，即光致发光（单分子）寿命、双分子复合系数、非辐射寿命和平衡自由载流子浓度。提取出的结果与通常在直接带隙半导体中获得的结果相当接近。该方法可能是深入了解ZnO中载流子复合过程以及获取有关ZnO激子动力学定量信息的有用工具。
