本论文针对高性能光通信和微波光子链路系统对相干平衡探测的新需求，开展了高速、高响应度、高共模抑制比平衡光电探测器单片集成芯片研究。与单个光探测器相比，平衡光电探测器芯片面临更高的响应度需求、更大的RC常数限制、更严苛的一致性问题。论文的主要工作及创新成果如下：针对台面型探测器高响应度与高速之间的矛盾，论文在保障高响应度的前提下，加快载流子输运并优化电路参数进而实现高带宽特性。首先，提出并验证了带有双崖层结构的光电探测材料结构，保障大电流条件下的光生载流子高速输运。其次，针对RC参数对带宽的限制，引入高阻抗CPW电极结构优化电路参数提升芯片带宽。研制出单个光电探测器最大带宽102 GHz，响应度0.63 A/W，与现有国际报道相同结构带宽为100 GHz的器件相比，响应度特性有显著提升。针对高阻抗CPW电极参数对探测器带宽特性的影响问题，提出了带有CPW电极多级分布参数的宽带光电探测器等效电路分析模型，并对带有常规50欧姆和115欧姆高阻抗CPW的探测器芯片进行了等效电路分析，突破了常规等效电路分析模型无法处理CPW部分的限制，支撑了高阻抗CPW提升器件带宽特性的机理分析，对设计高性能器件具有重要指导意义。针对单片集成平衡探测器的高共模抑制比特性，分别从关键制作工艺和评测技术开展了研究。首先，针对干法刻蚀导致的严重衬底漏电问题，引入干法加湿法腐蚀的工艺将衬底漏电由mA量级降低至百nA量级；其次，引入三台面探测器结构，增加了两个有源区尺寸一致性，从而保障了芯片的宽带高共模抑制比特性。在测试系统方面，针对普通拍频系统的频率、幅度稳定性差的问题，分别引入调制器载波抑制边带拍频产生信号方法、U型垂直光纤耦合装置，获得了频率、幅度稳定的信号。最终制作的单片集成平衡光电探测器带宽实现40 GHz，其宽谱共模抑制比特性在40 GHz范围内低于- 20 dB。在探测器高饱和特性理论分析方面，详细分析了热效应对器件饱和特性的影响。通过结合热阻分析模型以及实验分析，得出器件测量最大功率与器件直径成正比的结论。通过建立蒙特卡罗仿真模型分析不同温度下的载流子输运特性及其空间电荷效应，对高压大电流下的器件饱和特性不随电压增加而线性增加进行机理分析，为未来进一步通过散热改善器件饱和性能提供了理论支撑。
In this dissertation, the research on high-speed, high-response, high common-mode rejection ratio balanced photodiodes is carried out in response to the new requirements of high-performance optical communication and microwave optical link systems for coherent balance detection. Compared with a single photodiode, monolithic integrated balanced detectors face higher responsivity requirements, greater RC constant limits, and stricter consistency issues. The main results and innovations are shown as follows:In terms of high-speed and high-response performance, this dissertation increases the carrier transport speed and optimizes the RC circuit parameters to achieve high bandwidth characteristics also high responsivity. At first, a double-cliff structure is proposed and verified to ensure the high-speed transport of photo-generated carriers under high current conditions. Secondly, a high-impedance CPW electrode is optimized to improve the RC constant limited bandwidth. A single photodiode with a maximum bandwidth of 102 GHz and a responsivity of 0.63 A/W has been developed, which is significantly improved compared to the published reports on the responsivity characteristics of 100 GHz photodiodes.In order to analyze the effect of high impedance CPW electrode parameters on the detector bandwidth characteristics, an equivalent circuit analysis model of broadband photodiodes with multi-section distribution parameters is proposed, and detectors with conventional 50 ohm and 115 ohm high impedance CPW are analyzed based on the model. The equivalent circuit analysis breaks through the limitation that the conventional equivalent circuit analysis model cannot handle the CPW part, which supports the mechanism analysis of the high-impedance CPW to improve the device bandwidth characteristics, has important guiding significance for designing high-performance devices.In terms of high common-mode rejection ratio performance of BPDs, researches on key manufacturing processes and evaluation techniques are carried out. First of all, for the serious isolation leakage caused by dry etching, the combined dry and wet etching process is introduced to reduce the substrate leakage from the mA level to the order of 100 nA. Secondly, the introduction of three-mesa PD structure helps ensure the consistency of the active area, thus ensuring the high common-mode rejection ratiop performance. In terms of test system, we optimize the test setup and fiber coupling system to obtain stable amplitude and phase signals. The final balanced photodiodes shows a banwidth of 40 GHz and a large common-mode rejection ratio performance lower than - 20 dB up 40 GHz .In the aspect of the saturation characteristics of photodiode, the effects of thermal effects on PD’s saturation characteristics are analyzed in detail. By combining the thermal resistance analysis model and experimental analysis, it is concluded that the maximum power point of the device is proportional to the device diameter when the device diameter is greater than 4 μm. A temperature related Monte Carlo simulation model is established to analyze the carrier transport characteristics at different temperatures and the space charge effects at different temperatures. It helps to explain the experimental phenomenon of PD’s saturation characterisitics don’t increase linearly with reverse bias voltage.
