CAREER: Micromachining of Gallium Nitride and Related Materials for Microwave and Optoelectronic Applications

9875600Fay在GaN及其相关材料(如AlGaN、InGaN、InAlN)微机械加工研究的基础上，提出了一项综合的职业发展计划。提出了三种只能通过微加工方法实现的微波和光电应用微机械器件：内联式透射式微波功率传感器、压电辅助微波微机械开关和用于实现表面发射蓝色异质结二极管的任意曲线耳镜面。提出的研究工作包括开发必要的微机械加工工艺，包括开发和实施计算机化的潜水角度控制平台，用于利用光电化学湿法腐蚀产生任意形状的蚀刻侧壁。此外，还将对刻蚀反应动力学进行全面的表征，并开发一个工艺模型，将其包含在角度控制阶段的控制软件中，以便刻蚀弯曲表面和任意角度的表面。还将通过实验研究GaN和AlGaN的热导率和热电性能随A1摩尔分数的变化，以优化直列式透射式功率传感器的材料选择，并为这一新材料体系的电子能带结构提供更多的实验见解。在该材料系统中开发和示范可行的微加工技术，将对高功率高温微波电子学和短波长光电子学领域产生广泛的影响。内联式透射式功率传感器可与高功率GaN基HEMT集成，提供在非常宽的带宽上直接测量放大器输出功率的能力，而不需要大型耦合结构。压电辅助微波微机械开关有望提供与硅和其他III-V材料中的微机电开关相同的优点，但由于GaN的压电性和与高速、高功率GaN HEMT的可集成性，还具有更低的激活电压的优点。最后，任意曲线镜面技术将允许实现表面发射异质结构二极管，以极大地减轻为高密度光存储和显示应用而封装这些器件的困难。除了提供更容易封装的表面发射结构，而不是边缘发射二极管结构，通过使用角度可控的蚀刻平台来定制镜面的曲率的能力还允许控制发射器的远场强度图案的污点，从而消除了对体积大且难以对准的外部光学部件使光束循环的需要。本研究项目的活动范围包括许多本科生直接参与研究活动的机会。这些机会包括参与微机械制造工艺的开发、器件制造和验证，以及成品器件的微波和光电测试。来自这项工作的研究成果也将被纳入本科课程；由Fay教授教授的集成光电子学、无线通信和微波测量以及电子电路课程都将直接受益于这项工作的成果。学生还将有机会通过本系的高级设计顶峰课程参与到这个项目中；大量的制造工艺设计机会以及计算机化角度控制蚀刻阶段的实施非常适合为期一年的本科设计项目。这项计划支持的另一项计划是扩大费教授的电子爱好之夜计划，将更多来自大学其他系和学院的学生包括在内，并包括感兴趣的高中生和社区成员。

9875600FayAn integrated plan for career development based on research on micromachining of GaN and related materials (e.g. A1GaN, InGaN, InA1N) is proposed. Three micromachined devices for microwave and optoelectronic applications that can only be realized using micromachining approaches are proposed to demonstrate the technology: an inline transmissive microwave power sensor, a piezoelectrically assisted microwave micromechanical switch, and an arbitrary curvilin-ear mirror surface for the realization of surface emitting blue heterostructure diodes. The re-search work proposed includes development of the necessary micromachining fabrication pro-cesses, including the development and implementation of a computerized submersible angle-controlled stage for generating arbitrarily-shaped etch sidewalls using photoelectrochemical wet etching. In addition, a full characterization of the etch reaction kinetics will be performed, and a process model developed for inclusion into the control software for the angle-controlled stage in order to etch curved as well as arbitrarily angled surfaces. The thermal conductivity and thermo-electric properties of GaN and A1GaN as a function of A1 mole fraction will also be investigated experimentally both in order to optimize the material selection for the inline transmissive power sensor, as well as to provide additional experimental insight into the electronic band structure of this nascent material system. The development and demonstration of a viable micromachining technology in this material system will have wide-ranging impact on the fields of high-power and high-temperature microwave electronics as well as short-wavelength optoelectronics. The inline transmissive power sensor is designed to be integrable with high-power GaN-based HEMTs, providing for the ability to directly measure amplifier output power over very wide bandwidths without the need for large coupling structures. The piezoelectrically-assisted micro-wave micromechanical switch is expected to provide the same benefits as micro-electro-me-chanical switches in Si and other III-V materials, but with the added benefit of lower activation voltage due to the piezoelectric properties of GaN and integrability with high-speed, high-power GaN HEMTs. Finally, the arbitrary curvilinear mirror surface technology will allow the imple-mentation of surface-emitting heterostructure diodes to greatly ease the difficulty in packaging these devices for high-density optical storage and display applications. In addition to providing a more easily packaged surface-emitting structure rather than an edge-emitting diode structure, the ability to tailor the curvature of the mirror surface through the use of the angle-controlled etching stage also permits the control of the stigmation of the far-field intensity pattern of the emitter, eliminating the need for bulky and difficult-to-align external optical components to circularize the light beam.The educational programs that are included within the scope of activities of this research project include numerous opportunities for undergraduate students to participate directly in research activities. These opportunities include participation in the development of micromachining fabrication processes, device fabrication and verification, and microwave and optoelectronic testing of the finished devices. The research results originating from this work will also be incorporated into undergraduate course work; the Integrated Optoelectronics, Wire-less Communications and Microwave Measurements, and Electronic Circuits courses taught by Prof. Fay will all benefit directly through inclusion of results from this work. Students will also be given the opportunity to be involved in this project through the senior design capstone course in the department; the numerous opportunities for fabrication process design as well as imple-mentation of the computerized angle-controlled etching stage are well-suited for year-long undergraduate design projects. An additional program to be supported by this program is the expansion of Prof. Fay's Electronics Hobby Evenings program to include more students from other departments and colleges across the university as well as to include interested high school students and community members.***