Ge/SiO2光栅增强型Si基Ge光电探测器的研究

High performance top-illuminated Si-based Ge photodetector is a key device in Si-based optoelectronic filed. However, there are two disadvantages deteriorating the performance of the top-illuminated Si-based Ge photodetector: high dark current and the conflict between responsivity and bandwidth. The latter disadvantage prevent the top-illuminated Si-based Ge photodetector from obtaining high responsivity and high bandwidth at the same time. This project proposes a novel Ge/SiO2 grating enhanced Si-based Ge photodetector. To reduce dark current, high quality Ge will be micro-nano-scale selective grown in the gaps of a SiO2 grating on Si using ‘bottleneck effect’ of dislocation. Here, Ge is not only prepared as the light absorption material, but also combined with the SiO2 grating to be Ge/SiO2 high-index-contrast grating at the same time. This Ge/SiO2 grating is used to relax the conflict between responsivity and bandwidth by modulate the illuminated light field for increasing the light absorption in the thin Ge film. This project will research the mechanism of the illuminated light modulated by Ge/SiO2 grating, and the creation, transference, and evolvement of dislocations in Ge by selective epitaxy. The technology to selective epitaxial high quality Ge, the main origins and control methods of the dark current of the Ge/SiO2 grating enhanced Si-based Ge photodetector will be obtained. Top-illuminated grating enhanced Si-based Ge photodetector with low dark current density, high-responsivity, and high-bandwidth will be fabricated.

高性能的面入射Si基Ge光电探测器是Si基光电子领域不可或缺的核心器件，但目前的面入射Si基Ge探测器存在暗电流大以及受响应度和带宽之间相互制约而难以同时提高响应度和带宽，因而影响器件性能的进一步提高。本项目提出一种新颖的Ge/SiO2光栅增强型Si基Ge光电探测器结构。利用微纳尺度选择外延的位错截止效应，在SiO2光栅图形Si衬底上的空隙间生长高质量的Ge，以降低位错导致的暗电流。Ge作为光吸收材料的同时，与SiO2光栅构成Ge/SiO2高折射率差光栅，利用该光栅对入射光的调制作用增强薄层Ge的光吸收，以减缓响应度与带宽之间的相互制约。项目将重点研究该光栅对入射光场的调控机理；探明微纳光栅图形衬底上选区外延Ge时位错的产生、迁移和演化规律，获得高质量Ge的选区外延技术；掌握该Ge光电探测器的暗电流主要来源和抑制方法；研制出低暗电流、高响应、高带宽的光栅增强型面入射Si基Ge光电探测器。

随着硅基微电子器件尺寸的不断缩小，集成芯片中的电互连成为其性能提高的瓶颈。硅基光互连具有高速度、高带宽、低功耗、低成本等特点，被认为是解决电互连性能瓶颈的最有潜力的方案之一。在硅基光互连所需的器件中，锗硅近红外光电探测器及其阵列是完成光信号高速接收的核心器件。目前，锗硅探测器的研究主要集中在提高器件响应度、带宽，降低暗电流，以及提升和其他硅基器件的工艺兼容性。本工作主要有以下几个方面。研究了SOI 上的Ge/SiO2光栅的结构参数对器件性能的影响，获得优化的器件结构，设计出了高响应、高带宽的面入射Ge/SiO2光电探测器。器件的光栅周期为13和16时，光吸收效率可达到65%，带宽可以分别达到80 GHz和60GHz。采用选区外延、原位高温退火和原位硅原子层钝化等工艺有效地提高了硅基锗外延层的晶体质量，并制备出了高性能的面入射探测器，暗电流密度仅为4.6 mA/cm2，响应度分别为0.59A/W@1310nm和0.27A/W@1550nm，带宽达到48GHz，零偏压下即可实现40Gbps的光信号接收。制备出了高性能的波导型锗硅探测器，响应度为0.82A/W@1550nm，器件的3-dB带宽达到32GHz，在零偏压下即可实现40和50Gbps的光信号接收。我们将该波导型锗硅探测器阵列与25通道硅基阵列波导光栅（AWG）进行了片上集成，研制成波分复用光接收器芯片。该光接收芯片单通道可以实现50Gbps的数据接收，25通道的数据接收总量达到1.25Tbps。本研究为高性能锗硅探测器的研究提供了新的思路和方案支持，为硅基光电子集成提供了技术积累。