基于高铟异变结构的铟镓砷红外雪崩光电探测器波长扩展研究

Detectors in 1.6-2.6 μm wavelength range are widely used in applications such as remote sensing, spectroscopy analysis, ultra-low-loss optical fiber communication, bio-chemical diagnostic and etc. Currently, it is imperative to develop high bandwidth and highly sensitive avalanche photodetectors (APDs) in this band due to the fact that performances of the present detectors have severely limited the development of cutting-edge detection techniques. In this proposal, we put forward a novel Indium-rich APD structure based on metamorphic buffer layers under the separate absorption and multiplication regime, aiming to extend the cut-off wavelengths of InxGa1-xAs APDs into 1.6-2.6 μm. Problems encountered by the existing APDs in this band, e.g. low operating temperature, high dark current and low bandwidth, are likely to be overcome. Prototype devices with a cut-off wavelength of 2.2 μm and gain factors up to 50 have already been demonstrated in our pilot studies, which is a clear evidence of the feasibility of this research proposal. This project intends to run extensive studies on the design and optimization of the APD structures, the suppression of the dark currents, and the exploration of the avalanche behaviors in these lattice-mismatched materials, by combing the energy band engineering, the electric field engineering and multiple measurement techniques. Avalanche parameters of these Indium-rich materials including the saturation drift velocity, the impact ionization coefficient, the threshold energy and so on, will be obtained. In the meantime, physical connections between key APD performances and the lattice-mismatched material properties as well the device structure designs will also be unambiguously established. Finally, on that basis, single element APDs with cut-off wavelengths beyond 2.4 μm will be realized, supplying new material and technology foundation for the development of high performance APD in this wavelength range.

1.6-2.6 μm波段红外探测器在遥感成像、光谱分析、超低损耗光纤通讯和生化检测等领域都有重要应用，但目前其性能严重制约了该波段探测技术的发展，迫切需要发展高速高灵敏型雪崩探测器。本项目提出基于异变高铟组分InGaAs的波长扩展型雪崩探测器新结构，通过采用吸收层倍增分离型架构，解决该波段雪崩探测器的工作温度低、暗电流大、增益带宽低等问题。前期预研工作已演示了截止波长为2.2 µm的原型雪崩探测器并实现了增益，证明了该项目思路的可行性。本项目将结合能带工程、电场工程和多种测试手段，深入开展器件结构优化设计和暗电流抑制研究，探索失配材料在大电场下的雪崩行为，获得高铟材料的电子饱和漂移速度、碰撞离化系数、阈值能量等雪崩特性参数，建立器件的核心性能参数与失配材料特性和器件结构设计的关联。在此基础上获得截止波长大于2.4 µm的单元器件，为发展该波段高性能雪崩探测器提供新的材料和器件技术基础。

1-2.5 μm短波红外波段在光谱成像、光谱分析等领域有重要应用，其目前主流探测器为InSb PIN型和延伸波长InGaAs PIN型器件。该两类器件已发展成熟，但探测率仍不足，制约了该波段探测技术的发展，发展具有内增益的延伸波长InGaAs雪崩探测器对提升探测性能有重要意义。本项目基于异变高铟组分InGaAs材料，研究实现延伸波长的InGaAs雪崩探测器。主要研究内容包括器件整体结构设计、能带和电场理论计算、结构参数优化设计、材料外延生长、器件流片制备、暗电流抑制途径等，实现原型器件研制。成功研制出了InP基截止波长为2.25μm的波长延伸型InGaAs APD器件。分别验证了三种用于实现波长延伸APD的技术方案，包括InxGa1-xAs/InyGa1-yAs量子阱超晶格miniband吸收层、失配InxGa1-xAs吸收层加晶格匹配In0.52Al0.48As倍增层、以及双失配InxGa1-xAs吸收层加InxAl1-xAs倍增层。经过实验验证及科学细致的理论分析，结果表明，第二种技术方案具有远优于另外两种的优良器件性能。揭示了波长延伸InGaAs APD的核心关键在于降低倍增层和晶格失配吸收层中的位错缺陷密度和杂质缺陷浓度。通过本项目研究，解决了InGaAs 雪崩探测器相关的一系列关键基础材料和器件物理问题，包括高In失配InGaAs的载流子散射和弛豫动力学机理、p型III-V材料中的Be-O络合补偿机理、台面型InGaAs 雪崩探测器侧壁表面态漏电机制及刻蚀工艺、雪崩几率瓶颈及其解决方案、InGaAs APD性能与电场调控、失配InGaAs 雪崩探测器的缺陷态隧穿暗电流机制等。这些关键科学问题的解决为后续进一步研制高性能InGaAs 雪崩探测器积累了丰富经验和参考，为发展该波段高性能雪崩探测器提供新的材料和器件技术基础。