Lotkov Evgeniy S, Baburin Aleksandr S, Ryzhikov Ilya A, Sorokina Olga S, Ivanov Anton I, Zverev Alexander V, Ryzhkov Vitaly V, Bykov Igor V, Baryshev Alexander V, Panfilov Yuri V, Rodionov Ilya A
FMN Laboratory, Bauman Moscow State Technical University, Moscow, 105005, Russia.
Dukhov Automatics Research Institute, (VNIIA), Moscow, 127055, Russia.
Sci Rep. 2022 Apr 15;12(1):6321. doi: 10.1038/s41598-022-09973-5.
The Indium Tin Oxide (ITO) platform is one of the promising solutions for state-of-the-art integrated optical modulators towards low-loss silicon photonics applications. One of the key challenges on this way is to optimize ITO-based thin films stacks for electro-optic modulators with both high extinction ratio and low insertion loss. In this paper we demonstrate the e-beam evaporation technology of 20 nm-thick ITO films with low extinction coefficient of 0.14 (N = 3.7·10 cm) at 1550 nm wavelength and wide range of carrier concentrations (from 1 to 10 × 10 cm). We investigate ITO films with amorphous, heterogeneously crystalline, homogeneously crystalline with hidden coarse grains and pronounced coarsely crystalline structure to achieve the desired optical and electrical parameters. Here we report the mechanism of oxygen migration in ITO film crystallization based on observed morphological features under low-energy growth conditions. Finally, we experimentally compare the current-voltage and optical characteristics of three electro-optic active elements based on ITO film stacks and reach strong ITO dielectric permittivity variation induced by charge accumulation/depletion (Δn = 0.199, Δk = 0.240 at λ = 1550 nm under ± 16 V). Our simulations and experimental results demonstrate the unique potential to create integrated GHz-range electro-optical modulators with sub-dB losses.
氧化铟锡（ITO）平台是用于低损耗硅光子学应用的最先进集成光调制器的有前景的解决方案之一。在这条道路上的关键挑战之一是为具有高消光比和低插入损耗的电光调制器优化基于ITO的薄膜堆栈。在本文中，我们展示了在1550 nm波长下具有0.14的低消光系数（N = 3.7·10 cm）且载流子浓度范围宽（从1到10×10 cm）的20 nm厚ITO薄膜的电子束蒸发技术。我们研究了具有非晶、异质结晶、具有隐藏粗晶粒的均匀结晶和明显粗晶结构的ITO薄膜，以实现所需的光学和电学参数。在此，我们基于在低能量生长条件下观察到的形态特征报告了ITO薄膜结晶中氧迁移的机制。最后，我们通过实验比较了基于ITO薄膜堆栈的三个电光有源元件的电流 - 电压和光学特性，并得出由电荷积累/耗尽引起的ITO介电常数的强烈变化（在±16 V下，λ = 1550 nm时，Δn = 0.199，Δk = 0.240）。我们的模拟和实验结果证明了创建具有亚分贝损耗的集成GHz范围电光调制器的独特潜力。
