【作者】 焦世龙；

【导师】 叶玉堂；

【作者基本信息】 电子科技大学 ， 光学工程， 2008， 博士

【摘要】 单片光电子集成电路（OEIC:Optoelectronic Integrated Circuits）将激光器、光探测器等光电子器件与驱动电路、前置放大器、限幅放大器以及时钟与数据恢复电路等电子器件/电路部分或完整集成在同一衬底之上,以最大程度地减小互联寄生参数对集成单元整体性能的不利影响,并有利于提高其可靠性及实现小型化、轻量化的发展目标,在长距离大容量光纤通信、自由空间光通信、光接入网、大规模并行光学互联、光开关、光存储、星载光电系统、微小型光电传感等领域具有广泛的用途。美国、德国、日本等发达国家在单片OEIC领域的研究十分活跃,并且成就斐然,部分成果已实现商业化。鉴于单片OEIC良好的应用前景以及国内在这个领域与国外先进水平的巨大差距,我们开展了单片OEIC光接收机前端的研究工作,并取得了若干创新性成果,提高了国内在这个领域的研究水平,为今后开发面向实用的高性能单片OEIC器件奠定了坚实的基础。主要成果及相关研究内容如下:（1）研制出国内首个5Gb/s级单片OEIC光接收机前端芯片。该芯片由基于砷化镓（GaAs）衬底的金属-半导体-金属（MSM）光探测器和赝配高电子迁移率晶体管（PHEMT）分布式前置放大器组成,从材料外延到工艺流水均实现了国产化,探索出一条适合国内条件的单片OEIC技术途径;（2）解决了单片OEIC器件研制中的关键性技术难题——台面工艺与常规GaAsPHEMT单片微波集成电路（MMIC）工艺的兼容性问题,包括采用反应离子刻蚀（RIE）形成高度精确且工作面光滑平整的MSM光探测器台面的工艺、插指电极金属化及剥离工艺、台面与平面器件互连工艺等;（3）研制出国内首个基于0.5μm GaAs PHEMT技术的20GHz带宽分布式前置放大器芯片,带宽与PHEMT器件特征频率之比达2/3,最小噪声系数3.03dB,平均等效输入噪声电流密度14.6pA/Hz^1/2,输出1dB压缩功率13.7dBm,放大器10Gb/s工作状态良好;（4）重点研究了0.5μm T型栅GaAs PHEMT工艺技术的关键环节——欧姆接触工艺和肖特基势垒工艺,流片得到性能优良的PHEMT器件:50MHz～26.5GHz范围内的小信号增益12～4dB,特征频率32GHz,最高振荡频率超过80GHz;（5）深入研究了PHEMT器件噪声性能,得出最小噪声系数F_min、等效噪声电导g_n、最佳输入阻抗Z_opt等参数与器件本征参数与寄生参数的关系,提出了通过改善欧姆接触工艺和优化材料结构设计等方法以进一步提升PHEMT器件低噪声性能,并在此基础上确定了PHEMT器件低噪声工作点,用于本次分布式前置放大电路设计,测试结果证明了上述噪声分析的有效性;（6）深入研究了MSM光探测器热电子发射模型,从理论上解释了GaAs MSM光探测器的基本工作模式,得出三点重要结论:①器件暗电流取决于金属-半导体接触界面的空穴势垒高度以及外加偏置条件;②光探测器工作速率受外加偏置影响较大,器件正常工作电压应位于平带电压与击穿电压之间;③平带电压由材料掺杂浓度和电极间距决定的特点具有重要意义;（7）对MSM光探测器在片测试结果进行了深入分析,得出低场暗电流为欧姆传导电流、高场暗电流为SiN介质Fowler-Nordhem隧穿电流的结论,初步解释了单片OEIC光接收机前端噪声偏大的原因,对于今后优化相关工艺条件,改善单片OEIC器件性能具有重要意义。更多还原

【Abstract】 Monolithic Optoelectronic Integrated Circuits （OEIC） partially or fully integrate the optoelectronic devices, such as lasers or photodetectors, and the electronic devices or circtuits, such as drivers, preamplifiers, limiting amplifiers, clock and data recovery circuits and so on, onto a single substrate to minimize the adverse influences on the performances of the integrated unit due to the interconnections between devices, which will also benefit the reliability of the integrated unit and the realization of miniaturization and light-weighting, and so, OEIC will be very widely used in the fields of long haul and large capacity optical fiber communication, free space optical communication, optical access network, large scale parallel optical interconnection, optical switch, optical storage, satellite-borne optoelectronic system, microminiaturized optoelectronic sensor, and so on. Considerable interests has been focused on monolithic OEIC some developed countries such as the United States of America, Germany, Japan, and so on, and the outcomes are very advanced, some of which have already been commercialized.Due to the potential applications of monolithic OEIC and the very large gap between the researches in our homeland and those in the countries mentioned above, three projects about monolithic OEEC optical receiver front end have been carried out in our laboratory. Finally, we get some innovative results, which set a new record in our country and lay good foundations for future researches aiming at higher performances and practical uses. The main achievements and relative contents are listed below:1) The first 5Gb/s monolithic optical receiver front end chip in our country has been developed, which consists of a Metal-Semiconductor-Metal （MSM） photodetector and a distributed preamplifier based on Pseudomorphic High Electron Mobility Transistors （PHEMT） on a GaAs substrate. The material epitaxy and device fabrication are fully based on domestic technologies.2) As the key problem to monolithic OIEC device fabrication, the compatibility between mesa process and GaAs PHEMT MMIC process has been resolved, which consists of the formation of MSM photodetector mesa with precise height and smooth working face by Reactive Ion Etching, interdigital electrodes metallization and lifting off, and the interconnections between mesa and planar devices.3) The first distributed preamplifier with 20GHz bandwidth based on 0.5μm GaAs PHEMT technology in our country has been demonstrated. The ratio of bandwidth to PHEMT characteristic frequency reaches about 2/3, and the minimal noise figure and the average equivalent input noise current density keep as low as 3.03dB and 14.6pA/（Hz）^1/2, respectively. The output 1dB power compress point is 13.7dBm, and the preamplifier has a good functional mode under the input signal of 10Gb/s NRZ pseudo-random bit sequences.4) As the key technologies to 0.5μm T gate GaAs PHEMT, ohmic contact and Schottky barrier processes are emphasized, the fabricated PHEMT die has a gain of 12 4dB in the range of 50MHz～26.5GHz, with the characteristic frequency and the max oscillation frequency of 32GHz and over 80GHz, respectively.5) The noise performance of the PHEMT device is investigated in detail. The dependences of minimum noise figure F_min, equivalent noise conductance g_n and optimum input impedance Z_opt on the intrinsic and parasitic parameters of PHEMT have been discussed, and the low noise working point is also determined, which is used for the design of distributed preamplifier. The final measured results show that the noise analyses mentioned before are valid.6) The thermionic emission model of MSM photodetector are studied in detail, and the fundamental working mode of GaAs MSM photodetector are explained, resulting to three important conclusions: a) the dark current is determined by the hole barrier at the metal-semiconductor interface and bias. b) The working speed of MSM photodetector is strongly influenced by bias, and the normal bias should be in the range of flat-band voltage and breakdown voltage. c) The fact that the flat-band voltage is determined by the dopant concentration and interdigital electrode space is important to practical application.7) The on-wafer measured results of MSM photodetector are analyzed in detail, resulting to the conclusion that the dark current mechanism at low electrical field is ohmic conductance, while at high field, the dark current comes from the Fowler-Nordhem tunneling of traped electrons in SiN dielectric film. Based on this result, the somewhat larger noise current in monolithic OEIC front end can be explained roughly, which is important to the optimization of relative process for a better noise performance.更多还原