Xie Hua, Fang Shenghao, Zhao He, Xu Xiaoliang, Ye Ning, Zhuang Wei
Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, School of Physical Sciences, University of Science and Technology of China Jinzhai Road 96 Hefei Anhui 230026 P. R. China +86-551-63607574.
Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences Fuzhou Fujian 350002 China.
RSC Adv. 2019 Nov 4;9(61):35771-35779. doi: 10.1039/c9ra08172k. eCollection 2019 Oct 31.
The semiconductor zinc germanium diphosphide (ZnGeP) has wide applications in the infrared nonlinear optics (NLO) due to its high nonlinear optical coefficient, wide infrared transparency range and high thermal conductivity. Absorptions near the pump or generation wavelength limit the effectiveness of this materials, with their complicated microscopic origins remaining largely elusive. Most research on the absorption mechanism of ZnGeP focused on the defect effect, while the quasi-particle effect and exciton effect are significant as well. We herein carried out the studies of the electronic band structure and optical properties of ZnGeP crystal. The quasiparticle and excitonic effects were examined by comparing the results of PBE, GW approximation and Bethe-Salpeter equation. Quasiparticle effect was found to widen the quasi-direct band gap and increases the valence and conduction band dispersions, which mainly blue-shifts the imaginary part of the dielectric function. The increased band gap also leads to a broadened lineshape in the second order susceptibility. The excitonic effects significantly enhance the peak intensity in the long wave regime of the dielectric function and red-shift the peaks in the high energy regime, leading to the greatly improved agreement with experiment. Our results provided a microscopic guidance for improving ZnGeP's optical performance.
半导体二磷化锌锗（ZnGeP₂）因其高非线性光学系数、宽红外透明范围和高导热性，在红外非线性光学（NLO）领域有广泛应用。泵浦波长或产生波长附近的吸收限制了这种材料的有效性，其复杂的微观起源在很大程度上仍不清楚。大多数关于ZnGeP₂吸收机制的研究集中在缺陷效应上，而准粒子效应和激子效应也很显著。我们在此对ZnGeP₂晶体的电子能带结构和光学性质进行了研究。通过比较PBE、GW近似和贝叶斯 - 萨尔皮特方程的结果来研究准粒子和激子效应。发现准粒子效应拓宽了准直接带隙并增加了价带和导带的色散，这主要使介电函数的虚部发生蓝移。增加的带隙还导致二阶极化率的线形加宽。激子效应显著增强了介电函数长波区域的峰值强度，并使高能区域的峰值发生红移，从而大大提高了与实验的一致性。我们的结果为改善ZnGeP₂的光学性能提供了微观指导。
