基于光驱动的RF MEMS开关及自检测系统

论文总字数：31023字

摘 要

本文对砷化镓的光电导特性进行分析，研究了光注入和砷化镓物理特性改变对于光电导的影响。在研究砷化镓光电导的时变特性时，从光脉冲的宽度、强度、砷化镓中的载流子寿命和光衰减系数等角度进行分析，结果表明，光脉冲宽度会影响光电导的上升沿时间，其强度会影响峰值和光电导响应速度，载流子寿命与光电导的下降沿和拖尾时间相关。在纳秒激光注入条件的瞬态研究中，综合物理实际情况，确定了砷化镓材料的光电导峰值和谷值。

然后利用该瞬变的光电导特性，提出基于光驱动的RF MEMS开关的射频结构,并进行结构设计、仿真和优化。利用超短脉宽光脉冲，在砷化镓中产生大量的光生载流子，快速改变砷化镓的电导率；由于光生载流子会在极短的时间内复合，砷化镓材料会在半绝缘态与导体态的快速转换，实现开关的功能。在HFSS仿真设计中，由于砷化镓材料本征载流子对于电导的贡献，使得开关在关断状态仍然有信号泄露，因而通过优化砷化镓电极结构以降低在该状态下插入损耗，并指出叉指电极结构的优化方向。

其次，为了实现基于光驱动的RF MEMS开关的自检测，在原共面波导基的RF射频开关上搭载在线式MEMS微波功率传感器。当微波信号在CPW传输线上传输是，由于CPW自身的欧姆损耗而产生热量，基于Seebeck效应，利用热电偶结构将产生的热量转化为直流热电压，从而间接测量出待检测微波功率大小。利用COMSOL多物理场功能分析，优化和分析了MEMS微波功率传感器与基于光驱动的RF MEMS开关的射频性能，解释了关键结构参数对暗电流的影响，实现了低的插入损耗和回波损耗（lt;-20dB），从而在线检测光开关在断开时泄露功率大小和在导通状态时输出功率大小。

最后根据各条件的优化结构，建立基于光驱动的RF MEMS开关及自检测系统模型。

关键词：砷化镓，光电导，RF MEMS开关，微波功率传感器，自检测

Abstract

In this thesis, the photoconductivity of gallium arsenide is analyzed, and the effects of photo-injection and physical properties of gallium arsenide on photoconductivity are studied. When studying the time-varying characteristics of gallium arsenide photoconductive, the analysis is carried out from the angle of light pulse, the intensity, the carrier lifetime in gallium arsenide and the light attenuation coefficient. The results show that the optical pulse width affects the rise of photoconductivity. Along the time, its intensity affects the peak and photoconductive response speed, and the carrier lifetime is related to the falling edge and tailing time of the photoconductor. In the transient study of nanosecond laser injection conditions, the photoconductivity peaks and valleys of gallium arsenide materials were determined by comprehensive physical conditions.

Then, using the transient photoconductive characteristics, the RF structure of the optically driven RF MEMS switch is proposed, and the structure design, simulation and optimization are carried out. Using ultrashort pulse width light pulses to generate a large number of photogenerated carriers in gallium arsenide, rapidly changing the conductivity of gallium arsenide; since photogenerated carriers will recombine in a very short time, GaAs materials will manifest fast transition between the semi-insulated state and the conductor state realizes the function of the switch. In the HFSS simulation design, due to the contribution of the intrinsic carrier of the gallium arsenide material to the conductance, the switch still has signal leakage in the off state, so the insertion loss is reduced in this state by optimizing the gallium arsenide electrode structure. Point out the optimized direction of the interdigitated electrode structure.

Secondly, in order to realize the self-detection of the optical drive-based RF MEMS switch, an on-line MEMS microwave power sensor is mounted on the original RF signal switch of the RF-based waveguide. When the microwave signal is transmitted on the CPW transmission line, heat is generated due to the ohmic loss of the CPW itself, and based on the Seebeck effect, the generated heat is converted into a direct current thermal voltage by the thermocouple structure, thereby indirectly measuring the magnitude of the microwave power to be detected. Using COMSOL multi-physics function analysis, the RF performance of MEMS microwave power sensor and optical drive-based RF MEMS switch is optimized and analyzed. The influence of light sword structure parameters on dark current is explained, and low insertion loss and return loss are realized. (lt;-20dB), thereby detecting the amount of leakage power of the optical switch when it is disconnected and the output power when it is in the on state.

Finally, based on the optimized structure of each condition, a model based on optical drive RF MEMS switch and self-test system is established.

KEY WORDS: gallium arsenide, photoconductivity, RF MEMS switch, microwave power sensor, self-test

目 录

摘 要 I

Abstract II

第一章 绪论 1

1.1 微电子机械系统（MEMS） 1

1.2 射频微电子机械系统（RF MEMS） 2

1.3 砷化镓光电导开关的发展过程和应用 2

1.3.1 砷化镓光电导开关的研究背景 2

1.3.2 砷化镓光电导开关的研究现状 3

1.3.3 砷化镓光电导开关的应用 3

1.4 微波功率传感器的研究现状 4

1.5 本文的主要研究目的和研究内容 6

第二章 基于光驱动的RF MEMS开关物理特性 7

2.1 光生载流子的产生和复合 7

2.1.1 载流子产生模型 7

2.1.2 载流子复合模型 8

2.1.3 砷化镓电极结构 11

2.2 砷化镓电导率计算模型 12

2.3 电导率影响因素分析 16

第三章 基于光驱动的RF MEMS开关的结构设计 20

3.1 共面波导结构 20

3.2 HFSS仿真设计分析 22

3.2.1 CPW结构的光电导开关 22

3.2.2 S参数仿真仿真和结构优化 22

第四章 基于光驱动的RF MEMS开关的自检测系统 29

4.1 塞贝克效应 29

4.2 在线式微波功率传感器的工作原理 31

4.3 微波功率-热的仿真和优化 32

第五章 总结和展望 36

5.1 工作总结 36

5.2 工作展望 37

致谢 38

参考文献 39

第一章 绪论

1.1 微电子机械系统（MEMS）

微电子机械系统（MEMS）是一门横跨多个物理维度的综合集成系统，其中包含有机械原件、微型传感器、执行器等，这些器件涉及热学、电学、机械、声学、生物等领域，最终实现了电子和机械相关的功能。

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