Department DIIES, Mediterranea University, 89122, Reggio Calabria, Italy.
Institute of Applied Sciences and Intelligent Systems, Unit of Napoli. Napoli, 80131, Naples, Italy.
Sci Rep. 2023 Jun 23;13(1):10205. doi: 10.1038/s41598-023-37199-6.
The design of semiconductor-based photonic devices requires precise knowledge of the refractive index of the optical materials, a not constant parameter over the operating temperature range. However, the variation of the refractive index with the temperature, the thermo-optic coefficient, is itself temperature-dependent. A precise characterization of the thermo-optic coefficient in a wide temperature range is therefore essential for the design of nonlinear optical devices, active and passive integrated photonic devices and, more in general, for the semiconductor technology explored at different wavelengths, from the visible domain to the infrared or ultraviolet spectrum. In this paper, after an accurate ellipsometric and micro-Raman spectroscopy characterization, the temperature dependence of the thermo-optic coefficient ([Formula: see text]) for 4H-SiC and GaN in a wide range of temperature between room temperature to T = 500 K in the visible range spectrum, at a wavelength of λ = 632.8 nm, is experimentally evaluated. For this purpose, using the samples as a Fabry-Perot cavity, an interferometric technique is employed. The experimental results, for both semiconductors, show a linear dependence with a high determination coefficient, R of 0.9648 and 0.958, for 4H-SiC and GaN, respectively, in the considered temperature range.
基于半导体的光子器件的设计需要精确了解光学材料的折射率，而折射率在工作温度范围内并不是一个常数。然而，折射率随温度的变化，即热光系数，本身也是温度依赖的。因此，在很宽的温度范围内对热光系数进行精确的特性描述对于设计非线性光学器件、有源和无源集成光子器件以及更一般地对于在不同波长下探索的半导体技术是至关重要的，从可见光域到红外或紫外光谱。在本文中，经过精确的椭偏和微拉曼光谱特性描述后，在 632.8nm 的可见光谱范围内，从室温到 500K 的很宽温度范围内，实验评估了 4H-SiC 和 GaN 的热光系数([Formula: see text])随温度的变化。为此，使用样品作为法布里-珀罗腔，采用干涉技术。对于这两种半导体，实验结果都显示出在考虑的温度范围内具有高决定系数 R，分别为 0.9648 和 0.958，具有线性关系。
