Hydrogen in the Ultrawide Bandgap Semiconductor beta-Ga203

非技术描述：带隙大于氮化镓和碳化硅的半导体正在成为一类新的超宽带隙电子材料，用于高功率，深紫外和极端环境应用。尽管超宽带隙半导体在器件应用方面具有巨大的潜力，并且比传统半导体制造的器件有了数量级的改进，但人们对其电性能的基本潜在机制知之甚少。该项目特别关注氧化镓，这是一种半导体氧化物，带隙为4.9 eV，是高功率器件的有吸引力的候选者。尽管其应用前景广阔，但氧化镓仍未得到充分开发，影响其电性能的缺陷和杂质仍存在争议，这为影响技术的基础研究提供了令人兴奋的机会。氢杂质及其化学反应强烈地影响氧化镓的电子性质，这是本项目特别感兴趣的。氧化镓中缺陷和杂质的实验研究为学生解决材料物理中的重要问题提供了一个极好的机会，点燃了他们在科学和工程领域取得成功的激情。在本项目中，从在物理学中代表性不足的群体中招收学生的范围扩大了。技术描述：本项目主要对具有4.9 eV超宽带隙的半导体氧化物氧化镓中的氢杂质进行实验研究。氢是氧化物半导体中重要的杂质，它可以产生n型电导率，也可以补偿深层受体。虽然对氧化镓中氢的性质有一些理论上的预测，但这一领域的研究还处于起步阶段。氧化镓有望表现出新的行为并揭示新的缺陷物理。这项研究涉及一套互补的实验方法，旨在确定氢杂质如何影响氧化镓的电子特性，并测试理论预测。例如，振动光谱与自由载流子吸收的结合为研究氢中心提供了一种强大的策略，该策略将特定缺陷与它们引起的电导率联系起来。此外，研究了氢与其他缺陷（如镓空位）的相互作用，以探讨氢对这些深层受体的钝化作用。拉曼散射和光热电离光谱的加入提供了对没有红外吸收谱线的其他类型的氢（如分子氢）的访问，但尽管如此，它们在影响氧化镓电导率及其热稳定性的缺陷反应中起着重要作用。本研究的预期结果是对氧化镓中哪些氢中心是n型掺杂剂的基本理解，并研究氢如何与其他影响电子性质的缺陷相互作用。需要了解这些缺陷及其反应的基础科学，以便能够可靠地控制和设计氧化镓的电导率。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical description: Semiconductors with bandgaps larger than those of gallium nitride and silicon carbide are emerging as a new class of ultra-wide-bandgap electronic materials for high-power, deep-ultraviolet, and extreme-environment applications. Despite the tremendous potential of the ultra-wide-bandgap semiconductors for device applications, with orders of magnitude improvement over devices made from more conventional semiconductors, the fundamental underlying mechanisms of their electrical properties are poorly understood. This project is focused particularly on gallium oxide, a semiconducting oxide with a bandgap of 4.9 eV, that is an attractive candidate for high-power devices. In spite of its promising applications, gallium oxide remains underexplored, and the defects and impurities that affect its electrical properties remain controversial, opening exciting opportunities for fundamental research that impacts technology. Hydrogen impurities and their chemical reactions strongly affect the electronic properties of gallium oxide and are of particular interest in this project. Experimental studies of defects and impurities in gallium oxide provide an excellent opportunity for students to solve important problems in materials physics, igniting excitement that leads to a successful career in science and engineering. The recruiting of students from groups that are under-represented in physics is expanded in the present project.Technical description: This project is focused on experimental investigation of the hydrogen impurity in gallium oxide, a semiconducting oxide with an ultra-wide bandgap of 4.9 eV. Hydrogen is an important impurity in oxide semiconductors where it can give rise to n-type conductivity and can also compensate deep acceptors. While there are a few theoretical predictions for the properties of hydrogen in gallium oxide, the research in this area is in its infancy. Gallium oxide promises to show new behaviors and to reveal new defect physics. The research involves a complementary set of experimental methods, aiming to determine how hydrogen impurities affect the electronic properties of gallium oxide and to test the theoretical predictions. For example, the combination of vibrational spectroscopy with free-carrier absorption provides a powerful strategy for studying hydrogen centers that relates specific defects with the conductivity they cause. Furthermore, the interactions of hydrogen with other defects such as gallium vacancy are investigated to probe the passivation of these deep acceptors by hydrogen. The addition of Raman scattering and photo-thermal ionization spectroscopies provide access to additional types of hydrogen species that do not have infrared absorption lines (such as molecular hydrogen) but that, nonetheless, play an important role in defect reactions that affect the conductivity of gallium oxide and its thermal stability. The expected outcome of this research is fundamental understanding of which hydrogen centers are n-type dopants in gallium oxide and investigates how hydrogen interacts with other defects that also affect electronic properties. The fundamental science of these defects and their reactions needs to be understood so that the conductivity of gallium oxide can be reliably controlled and engineered.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.