超薄倍增层雪崩光电探测器的增益带宽噪声及高速器件研究

With the continuous development of various communication services, the capacity of optical communication network is still growing rapidly. The demand for high-speed and high-sensitivity avalanche photodetector (APD) is increasing, but the progress of APD performance is lagging behind in the growing Requirements. Much more effort is needed to improve the APD properties. In recent years, it has been found that APD uses ultra-thin multiplication layer to improve the device gain bandwidth product while reducing the noise. The excess noise depends not only on the properties of the multiplier layer material (such as hole and electron ionization coefficient), but also on the thickness. The use of ultra-thin multiplication structure is a feasible way to improve the performance level of existing APD devices. The project aims to use the Monte Carlo and finite element numerical methods and the more essential material properties (such as band structure, carrier effective masses, phonon scattering probability, ionization energy, etc.) to describe the high-speed low-noise APDs’ performance (such as gain, bandwidth, excess noise, and detection sensitivity, etc.) , and find the optimization rules of the device. At the same time, we will study the device noise test method, hope to obtain accurate excess noise to describe the device performance properly. Through the above research, we will complete the innovative photomultiplier devices using high-performance materials and high-speed device structure, get ultra-high gain bandwidth product separation-charge-absorption-multiplication-collection APD, and greatly enhance the current research to a higher level.

随着各种通信业务的不断发展, 光通信网络的容量仍在快速增长，对高速、高灵敏度雪崩光电探测器（APD）的需求不断上升，但目前APD性能远滞后于日益增长的要求，亟待研究提高。近年研究发现，APD过剩噪声不仅依赖于倍增层材料性质（如空穴、电子离化率系数），还依赖于倍增层厚度，采用超薄倍增层可提高器件增益带宽积并减小噪声。本项目拟从更本质的材料特性（如带隙、载流子有效质量、声子散射几率、碰撞电离能等）和结构参数出发，采用蒙特卡洛和有限元的数值法将结构和材料参数统一起来，以更接近物理本质的参数和概念来描述高速低噪声APD的性能（如增益、带宽、过剩噪声和探测灵敏度等），以寻找器件优化规律；同时研究器件噪声的测试方法，精确获得过剩噪声，以正确评估器件性能。通过以上研究，拟构建采用高性能材料和高速器件结构的创新性APD器件，得到超高增益带宽积分离吸收电荷倍增收集型APD测试结果,大幅提升目前研究水平。

目前是一个信息和信息技术大爆炸的时代，光通信容量的需求不断刷新。高速高灵敏度的探测在中长距无源光网络、5G通信和大的数据中心有非常迫切的要求。本项目在此背景下研究了光通信波段高速高增益的InAlAS/InGaAs高速APD，对器件有了非常深入的研究，（1）采用有限元分析法对台面APD性能进行了系统模拟研究，建立了SAGCMCT结构的背入射台面APD仿真模型模拟APD内光电转换以及载流子的输运过程，采用3D模型精确计算了器件电容，完成结合渡越时间和外部RC时间的一体化光脉冲时间响应模拟，形成完备的APD器件带宽模拟。（2）优化了高速高增益器件外延结构，突破钝化工艺和高精度倒装键合工艺，完成三级台阶结构的低电流低噪声APD器件。（3）实际测试结果表明，采用0.12μm的InAlAs倍增层，有源区直径14μm的背入射APD，在0.9倍击穿电压下的暗电流仅6.7nA，带宽达到25GHz（M=1）和20GHz（M=5），增益带宽积线性部分达到270GHz。(4)对APD器件的噪声进行了理论和实验研究，并和InP器件进行了对比，表明InAlAs-APD的k因子在0.1~0.2之间，远低于InP-APD，测噪声大幅降低。（5）相关研究结果发表论文3篇，专利2项。本项目经过4年的研究高质量完成了相关研究任务，基本达到预期目标。