Collaborative Research: Defects and Dopants in Critical Wide Band Gap Semiconductors - ZnO, InGaZnO, Ga2O3 and ScN

非技术描述：该项目探索半导体中氧化锌、氧化镓、氧化铟镓和氮化钪原子尺度缺陷的电子和化学性质，并特别关注控制这些缺陷，以实现更高的功率、速度和光输出。这些缺陷可能通过捕获电荷载流子来降低电流和充电速度，从而降低半导体性能。这些缺陷敏感地取决于用于生长和/或随后的热、化学和等离子体处理的特定技术。该研究将实验研究与输运模型相结合，旨在测量这些相对未开发的半导体的晶格结构和化学缺陷的光学特性，使用生长变化，等离子体，氢退火和辐照处理来确定其物理性质，并在磁场中进行电学测量以确定其捐赠或接受电子的能力。项目的最终目标是了解这些缺陷的本质，并最终消除它们。消除这些结构和/或化学缺陷的能力影响了一系列技术。氧化锌是取代目前太阳能电池、数字显示器和发光二极管中高成本材料的主要候选材料。氧化镓处理非常高电压的能力可以改善电信和电力传输的电源开关。氧化铟镓可以提供更高速度的显示和高分辨率电视。氮化钪可以降低手机中使用的半导体金属触点的电阻和功耗。这些活动为一名研究生、几名大学本科生和一所女子高中的高中生提供了合作研究的机会。技术描述：研究重点是对半导体材料ZnO、Ga2O3、InGaZnO和ScN的原生点缺陷进行基础研究，这些材料已成为先进的高功率和光电子显示应用的关键材料。ZnO掺杂Ga或Al，是取代昂贵的氧化铟锡在太阳能电池、显示器、发光二极管和触摸屏中的首选材料。Ga2O3具有创记录的高击穿电压，是电力开关的主要新材料。InGaZnO是显示器和高分辨率电视（如夏普）中取代非晶硅晶体管的主要非晶氧化物。ScN可以改善gan基器件的欧姆接触，并作为GaN-on-Si技术的缓冲层。这四种材料都可以高度掺杂杂质供体，但它们都受到深层缺陷的影响，这些缺陷会补偿自由载流子并引入散射，从而降低载流子的迁移率。Ga2O3、InGaZnO和ScN以及ZnO中原生点缺陷的性质几乎完全未知，但这些缺陷会对载流子密度、迁移率和界面输运产生重大影响。研究团队将利用三维纳米尺度光谱，结合施主/受体密度和介电特性，分别通过温度依赖的霍尔效应和反射/透射测量来测量特定缺陷的空间分布和物理性质，以便在近纳米尺度上识别和量化缺陷密度，并了解如何通过新的生长和加工技术来控制它们。本工作的目标是了解这些化合物中限制简并掺杂和产生较低迁移率的主要补偿缺陷，结合近表面远程等离子体，植入和热加工与光学和表面科学技术来识别这些原生点缺陷，将它们与供体/受体密度相关联，并化学控制它们。该项目还旨在探索这些缺陷对涉及这些半导体的肖特基势垒和异质结的势垒和输运的影响。该项目的总体目标是通过选择提高导电性和界面性能的生长和加工技术来控制这些缺陷及其对载流子密度和结输运的影响。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: The project explores the electronic and chemical properties of atomic-scale imperfections in the semiconductors zinc oxide, gallium oxide, indium gallium oxide, and scandium nitride with a specific focus on controlling such defects for higher power, speed, and light output of advanced electronic devices. Such defects may degrade semiconductor properties by trapping charge carriers to reduce the current and charge speed. These imperfections depend sensitively on the specific techniques used for growing and/or subsequent thermal, chemical, and plasma treatments. The research, which combines experimental studies with transport modeling, is aimed at measuring the optical properties of lattice structural and chemical imperfections of these relatively unexplored semiconductors, using growth variations, plasma, hydrogen annealing, and irradiation treatments to identify their physical nature and electrical measurements in magnetic fields to identify their ability to donate or accept electrons. The project ultimate goal is to understand the nature of these defects and eventually to eliminate them. The ability to remove these structural and/or chemical defects impacts a range of technologies. Zinc oxide is a prime candidate to replace today's high-cost materials in solar cells, digital displays, and light emitting diodes. Gallium oxide's ability to handle very high voltages can improve power switches for telecommunications and power transmission. Indium gallium oxide can provide higher speed displays and high-resolution TVs. Scandium nitride can lower resistance and power consumption of metallic contacts to semiconductors used in cellphones. The activities provide collaborative research opportunities for a graduate student, several university undergraduates, and high school students from an all-girl's high school.Technical description: The research focuses on fundamental studies of native point defects in the semiconductors ZnO, Ga2O3, InGaZnO, and ScN, which have emerged as critical materials for advanced high power and optoelectronic display applications. ZnO, doped with Ga or Al, is the prime candidate to replace expensive indium tin oxide in solar cells, displays, light emitting diodes, and touchscreens. Ga2O3 is the dominant new material for power switches because of its record high breakdown voltage. InGaZnO is the dominant amorphous oxide replacing amorphous-Si transistors in displays and high-resolution TVs (e.g., Sharp). ScN can improve ohmic contacts in GaN-based devices and serve as a buffer layer for GaN-on-Si technology. All four can be highly doped with impurity donors, yet all four are impacted by deep level defects that compensate free carriers and introduce scattering that reduces carrier mobility. The nature of native point defects in Ga2O3, InGaZnO, and ScN as well as ZnO is almost completely unexplored, yet these defects can have a major impact on carrier density, mobility, and interface transport. The research team will measure the spatial distribution and physical nature of specific defects using 3-dimensional nanoscale optical spectroscopies coupled with donor /acceptor densities and dielectric properties by temperature-dependent Hall effect and reflectance/transmission measurements, respectively, in order to identify and quantify defect densities on a near-nm scale and understand how to control them through new growth and processing techniques. The goals of this work are to understand the primary compensating defects in these compounds that limit degenerate doping and produce lower mobilities, combining near-surface remote plasma, implantation and thermal processing with optical and surface science techniques to identify these native point defects, correlate them with donor/acceptor densities, and chemically control them. The project also aims to explore the impact of these defects on barriers and transport at Schottky barriers and heterojunctions involving these semiconductors. The overall goal of the project is to control these defects and their impact on carrier densities and junction transport by selected growth and processing techniques that improve conductivity and interface properties.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.