基于氮化硅波导的垂直型锗硅电吸收调制器的研制及其机理研究

The high speed optical modulator is the key element in Silicon Photonics. The modulator is required to achieve higher speed, smaller footprint, lower power consumption and higher integration density in order to achieve the board-to-board, chip-to-chip and even inter-chip optical connection. This project proposes a new vertical germanium silicon (GeSi) electroabsorption modulator (EAM) based on silicon nitride waveguides. This modulaor has the potential to work under lower voltage swing and thus lower power consumption with the advantages of high speed, small footprint and high integration density. It is highly possible that the GeSi EAM can be used in the next generation silicon photonics chips for the optical communication in the shorter distance. In this project, we will study the vertical p-i-n structure and its effect to electrical field intensity together with the process parameters. We can then analyze the relationship between the EAM performance and the structure/process parameters. We will also optimize the coupling loss between silicon nitride waveguides and the EAM waveguides by understanding the mode mismatch. This project will develop compatible GeSi epitaxy process based on the existing silicon photonics platform, study the effect of the silicon content on the bandgap of the GeSi material, fabricate the EAM chips and then perform the measurement and data analysis. We aim to achieve a 3dB bandwidth of 40GHz electroabsorption modulator working under 1.5V voltage swing and the wavelength from 1535nm to 1565nm.

高速调制器是硅基光电子技术中的核心器件之一。为了实现板间互连、片间互连甚至到片内互连，硅基光电子集成电路对调制器的速率、体积、功耗和集成度有非常高的要求。本项目提出一种新型的基于氮化硅波导的垂直型锗硅电吸收调制器。这种调制器具有在更低驱动电压下工作的潜力，功耗更低，同时也具备速率高、体积小和集成度高的优势。本项目拟研究基于氮化硅波导的垂直型锗硅电吸收调制器结构，以及该结构和工艺参数对调制器内电场强度的影响，从而分析结构和工艺参数对调制器性能的影响。通过结构的优化设计，降低氮化硅波导与调制器波导的耦合损耗。此外，本项目还将基于现有的硅光工艺平台，研发与之兼容的锗硅外延工艺，定量分析硅含量与材料带隙的关系，制备基于氮化硅波导的锗硅电吸收调制器芯片，并对该芯片进行测试和分析，以实现可在1.5V驱动电压和1535nm~1565nm波段下工作的锗硅电吸收调制器，3dB带宽达到40GHz。

高速调制器是硅基光电子技术中的核心器件之一。为了实现板间互联、片间互联甚至到片内互联，硅基光电子集成电路对调制器的速率、体积、功耗和集成度有非常高的要求。电吸收（EA）调制器基于Franz-Keldysh（FK）效应，具有较小的尺寸和简单的电极结构，能耗较低的同时有非常高的带宽和调制速率。本项目首先开展高质量的选择性锗硅外延生长的研究，分析外延生长条件与锗硅材料能带的定量关系。 然后对EA调制器的FK效应进行理论性探究，并对器件的耦合结构进行优化设计。之后对水平型和垂直型EA调制器进行器件设计仿真，水平型EA调制器在1550nm处的插入损耗达到2.84dB，消光比达到6dB，FOM（消光比/插入损耗）达到2.12，垂直型EA调制器器件理论FOM达到1.64，3dB截至频率达到75.65GHz。最后通过优化工艺流程步骤，研制了L波段高FOM(2.47)及大带宽(>67GHz)性能的纯锗EA调制器。首次实现了片上热调结构以拓宽器件的光学带宽，器件具有1.71的FOM和88.99GHz的大带宽。不加片上热调时光学带宽达到1535~1565nm，加上片上热调后光学带宽拓展可扩展至1600nm（1600nm为测试设备激光器的极限波长）。