Ge/Si异质结纳米线雪崩倍增探测器的制备及性能研究

传统Ge/Si吸收倍增分离雪崩探测器(SACM-APD)面临着工作电压高、波导光耦合效率低等问题。研制高性能纳米线光电探测器是当前光信息技术前沿的热点课题之一，为解决上述局限提供了新的思路。本项目创新提出Ge/Si异质结纳米线SACM-APD器件结构，着重对Ge/Si纳米线材料的生长质量、纳米线器件的设计、制备工艺、工作机理展开细致研究；探索Ge/Si纳米线APD器件结弯曲效应增强内电场、径向结实现光吸收和载流子输运的高效分离、雪崩倍增效应、隧穿激发等物理机制；分析Si纳米线径向Ge壳层外延过程中应变弛豫和位错动力学机制，优化平基底上低位错密度Ge/Si薄膜垂直均匀刻蚀的工艺条件，获得高质量的Ge/Si径向和轴向异质结纳米线材料；研究纳米线表面缺陷处理、表面钝化、纳米线与体材料隔离等器件工艺，揭示纳米线器件中载流子的复合输运机制，研制出低功耗和高性能Ge/Si异质结纳米线APD器件。

Conventional Ge/Si separated absorption charge multiplication-avalanche photodetector (SACM-APD) is faced with two problems, high operating voltage and low optical coupling efficiency for waveguide-integrated structure. The appearance of novel nanowire photodetector provides a new way to solve these problems. Thus, the fabrication of high-performance nanowire SACM-APD is one of the frontier topics in optoelectronic information field. The SACM-APDs based on Ge/Si axial and coaxial heterojunction nanowire are innovatively proposed in this project. The quality of Ge/Si axial and coaxial heterojunction nanowire, the design of device configuration, the device processing and the operating mechanism of those nanowire SACM-APD are studied in detail, respectively. The physical mechanisms of an increase in internal electric field induced by junction curvature effects, efficient separation of light absorption and carrier collection arisen from the coaxial heterojunction structure, avalanche multiplication effects in Ge/Si axial and coaxial heterojunction nanowire, and the tunneling properties of carriers are also investigated. Analysis on the strain relaxation and the dynamic mechanisms of dislocations during the growth of Ge shell layer on Si core-nanowire provides the theoretical guidance for the suppression of dislocation nucleation and diffusion. The process conditions for vertical uniform etching of Ge/Si films with low dislocation density are optimized. High quality Ge/Si axial and coaxial heterojunction nanowires are obtained. The device processing technologies, including the surface defect treatment of nanowires, nanowire surface passivation and the separation process of nanowire and bulk material, are studied. The recombination and transport mechanisms of carriers in nanowire device are revealed. Low-power-consumption and high-performance Ge/Si heterojunction nanowire SACM-APDs are fabricated.