Impact Ionization Coefficients in Ga2O3

非技术性描述：该项目的重点是宽带隙半导体氧化镓的基本材料特性，它在一系列电气和光学系统中显示出前景。由于这是一种相对未开发的材料，因此需要确定其基本特性，包括对于理解材料在高电场下的行为非常重要的参数。这项研究特别涉及碰撞电离系数，目前还没有通过实验确定。拟议的研究计划是在不同的电场和温度下处理这些参数，并将其与其他半导体材料中高压行为的既定理论进行比较。该研究结合了实验研究和高级模拟，旨在对电子和空穴在这种有前途的宽带隙半导体中的行为方式进行基本了解。缺陷和杂质对这种材料的高电压特性的作用影响了一系列技术，包括电动汽车和相关充电基础设施中的功率控制电子设备，紫外线发射器和检测器以及高频/高温电子设备。活动为一名研究生和几名本科生提供了合作研究的机会，也吸引了来自代表性不足的群体和经济弱势背景的高中生。技术说明：研究重点是击穿机制的基础研究和常见缺陷类型及其密度对镓氧化物中载流子倍增的作用。这对于高功率、高温系统应用是有前景的材料。该提案将建立基本的材料参数及其电场和温度依赖性，这是理解氧化镓中载流子传输和倍增机制所需的。在高电场和温度范围内的氧化镓中的电子和空穴传输的基本关系需要通过实验来建立。更具体地说，实验研究的重点是检查的温度依赖性的碰撞电离系数使用载流子注入到结构，偏置在各种电压，以建立一个电场。在这种条件下预期的载流子倍增效应也会受到材料中缺陷的类型和密度的影响，这需要通过检查具有不同缺陷密度的样品来量化。该研究采用了电气表征技术，包括温度依赖性电流-电压和扩散长度测量，并使用透射电子显微镜进行结构分析和化学分析，以详细了解缺陷如何影响氧化镓在高压下的击穿特性。实验支持先进的电气模拟作为温度和电压的函数，用于研究这些参数对载流子的碰撞电离和通过氧化镓层的传输的预期影响。这些研究正在建立传输参数，这不仅与基础材料科学有关，也与理解基于氧化镓的功率电子器件和日盲光电探测器的高温运行有关。该奖项反映了NSF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 is focused on fundamental materials properties of wide bandgap semiconductor, gallium oxide, which shows promise in a range of electrical and optical systems. Since this is a relatively unexplored material, there is a need to establish its basic properties, including parameters that are important for understanding how the material will behave under high electric fields. The research is particularly addressing the impact ionization coefficients, which are currently not established experimentally. The proposed research plan is tackling these parameters at different electric fields and temperatures and is comparing them to the established theory for high voltage behavior in other semiconductor materials. The research, which combines both experimental studies and advanced simulations, is aimed at developing a fundamental understanding of the way in which electrons and holes behave in this promising wide bandgap semiconductor. The role of defects and impurities on the high voltage characteristics of this material impacts a range of technologies including power control electronics in electric vehicles and associated charging infrastructure, ultraviolet emitters and detectors and high frequency/high temperature electronics. The activities provide collaborative research opportunities for a graduate student and several undergraduate students and also engages high school students from underrepresented groups and economically disadvantaged backgrounds.Technical description: The research focuses on fundamental studies of the breakdown mechanism and the role of common defect types and their density on carrier multiplication in gallium oxide. This is a promising material for high power, high temperature systems applications. This proposal will establish basic materials parameters and their electric field and temperature dependence, which are needed to understand the carrier transport and multiplication mechanisms in gallium oxide. The fundamental relations governing the electron and hole transport at high electric fields and over a range of temperatures in gallium oxide needs to be established experimentally. More specifically, the experimental studies focus on examining the temperature dependence of impact ionization coefficients using carrier injection into structures which are biased at a variety of voltages to establish an electric field. The carrier multiplication anticipated under such conditions effect can also be affected by the type and density of defects in the material and this needs to be quantified by examining samples with different defect densities. The research employs electrical characterization techniques, including temperature-dependent current-voltage and diffusion length measurements, with structural analysis using transmission electron microscopy with chemical analysis to provide detailed insights on how defects affect the breakdown characteristics of gallium oxide at high voltages. The experiments are supported by advanced electrical simulations as a function of temperature and voltage, which are used to study the expected influence of these parameters on impact ionization of carriers and transport through the gallium oxide layers. The studies are establishing the transport parameters, which are relevant not only for the basic materials science but also for understanding high temperature operation of gallium oxide based power electronics and solar-blind photodetectors.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.