This thesis work features the exploration of the capabilities and limitations of devices based on MBE (Molecular Beam Epitaxy) grown IIInitride materials under three principal applications: photovoltaics, high electron mobility transistors (HEMTs), and terahertz emitters. InGaN solar cells covering the deep UV to the red ranges of the solar spectrum were fabricated. The increase in indium composition in the alloys to absorb longer wavelengths resulted in considerable leakage and series resistance caused by a combination of surface electron accumulation and electrically active line defects. A combination of thermal annealing, improved ohmic contact metal selection, electrochemical anodization, and grain coarsening resulted in improved performance. Higher sheet densities and sheet current with minimal leakage was obtained in an AlGaN/GaN HEMT by optimizing the design to include a GaN cap as a tunneling barrier and an AlN interbarrier to increase 2DEG confinement. Furthermore, a novel technique using a 325 nm, surface sensitive laser to perform micro-Raman thermal mapping on HEMTs was developed. The technique utilized higher order A1(LO) phonons for higher thermal sensitivity. Lastly, progress was made toward GaN THz emitter development by achieving low series resistance operation through improved metal contact selection and ultra high Ge donor doping via MBE.
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机译：本论文的工作旨在探索基于MBE（分子束外延）生长的III族氮化物材料的器件的性能和局限性，这些器件主要用于以下三个主要应用：光伏，高电子迁移率晶体管（HEMT）和太赫兹发射器。制作了覆盖深紫外到太阳光谱红色范围的InGaN太阳能电池。合金中铟成分的增加以吸收更长的波长会导致大量的漏电和串联电阻，这是由于表面电子积累和电活性线缺陷共同引起的。热退火，改进的欧姆接触金属选择，电化学阳极氧化和晶粒粗化的组合可提高性能。通过优化设计，包括一个GaN帽作为隧道势垒和一个AlN势垒来增加2DEG的限制，在AlGaN / GaN HEMT中获得了更高的板密度和最小漏电流。此外，还开发了一种使用325 nm表面敏感激光器在HEMT上进行微拉曼热成像的新技术。该技术利用了更高阶的A1（LO）声子来提高热灵敏度。最后，通过改进的金属接触选择和通过MBE的超高Ge施主掺杂实现低串联电阻操作，在GaN THz发射极开发方面取得了进展。
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