Traps in MBE-grown III-Nitride FET Structures on SiC

智能优点：对体相、表面和异质结界面处存在的陷阱缺乏足够的知识，是阻碍高功率III-氮化物化合物半导体微波器件发展的主要障碍之一。拟议的基础研究旨在识别陷阱(即在相对于带边的带隙中找到它们的能量，它们的俘获截面和来源)，这些陷阱深刻地影响着MBE生长的III-氮化物GaN MESFET、AlGaN/GaN HEMTs和AlInGaN/InGaN HEMTs的漏极电流崩溃、增益压缩、栅漏滞后、跨导频散和漏极电导等器件特性。识别这些器件结构中的陷阱对于优化器件设计、生长和工艺条件，从而最大化高功率微波性能是非常重要的。一旦AlInGaN/InGaN HEMT的设计、生长和工艺条件得到优化，预计它们将产生创纪录的功率性能。将制作一系列样品，只有一种生长/处理条件(生长温度、表面钝化等)。或器件设计特征(合金成分、层厚度等)每一组都不同，保持所有剩余条件相同。所有器件将首先针对其DC和脉冲漏极电流-漏极电压-栅极电压性能进行表征，包括栅极滞后和漏极滞后；在不同偏置条件和频率下作为输入功率函数的输出功率、增益和功率附加效率性能；然后是器件结构中的陷阱。陷阱将通过漏电流和栅电容深能级瞬变光谱、光电离光谱以及跨导和输出导纳频散测量来研究。通过对实验数据的分析，将确定陷阱相对于带边的能量位置、俘获截面和浓度。陷阱测量也将在承受短期和长期偏置应力的器件上进行。对于每组样品，器件性能和陷阱测量结果以及该组样品中生长/处理/设计参数的变化程度将被关联，以识别导致特定器件性能量恶化的陷阱/陷阱；陷阱/陷阱的来源；以及可以将陷阱浓度降至最低的生长、加工和设计条件。更广泛的影响：拟议的工作是一项仔细、详细的基础研究，需要仔细的实验和分析。这项工作的结果将通过提供最佳的生长和工艺条件以及获得最高器件性能所需的器件设计特征，对推进高功率微波III-氮化物化合物半导体器件技术产生立竿见影的影响。这项工作将与海军研究实验室(NRL)的III-氮化物装置研究小组合作进行。15年多来，PI一直与NRL的科学家在NSF支持的项目上成功合作。这个项目为学生提供了一个极好的机会，让他们在一个著名的政府实验室中，在一个重要的研究课题上，使用最先进的器件生长、加工和表征设备，获得实践经验。这一经历为学生在工业和政府领域的职业生涯做好了充分的准备。研究生和本科生都将参与这项拟议的研究。

Intellectual Merit: A lack of sufficient knowledge on traps, which are present in bulk, at surface, and at heterojunction interfaces is one of the main obstacles for the progress of high-power III-nitride compound semiconductor microwave devices. The proposed basic research is aimed at identifying the traps (i.e. finding their energy in the bandgap with respect to a band edge, their capture cross-section and origin), which profoundly effect the device characteristics such as: drain current collapse, gain compression, gate and drain lag, frequency dispersion of transconductance and drain conductance of MBE-grown III-nitride GaN MESFETs, AlGaN/GaN HEMTs, and AlInGaN/InGaN HEMTs. Identification of traps in these device structures is very important for optimizing the device design, growth, and processing conditions and consequently for maximizing high-power microwave performance. The AlInGaN/InGaN HEMTs are projected to yield record power performance once their design, growth, and processing conditions are optimized. A series of sets of samples will be fabricated, with only one growth/processing condition (growth temperature, surface passivation etc.) or a device design feature (alloy composition, layer thickness etc.) varied in each set keeping all the remaining conditions same. All devices will be characterized first for their DC, and pulsed drain current-drain voltage-gate voltage performance including the gate-lag and drain-lag; output power, gain and power added efficiency performance as a function of input power at various bias conditions and frequencies; and then for traps in the device structure. The traps will be studied by drain-current and gate capacitance deep level transient spectroscopy, photoionization spectroscopy, and transconductance and output-admittance frequency dispersion measurements. Energy location of the traps with respect to the band edges, their capture cross-section and concentration will be determined by analyzing the experimental data. Trap measurements also will be performed on devices subjected to short and long-term bias stress. For each set of samples the device performance and trap measurements results, and the extent of change in growth/processing/design parameter in that set of samples will be correlated to identify the trap/traps responsible for deterioration of a specific device performance quantity; origin of the trap/traps; and the growth, processing and design conditions, which can minimize the trap concentration. Broader Impacts: The proposed work is a careful, detailed basic research, which requires careful experimentation and analysis. Results of this work will have an immediate impact on advancing high-power microwave III-nitride compound semiconductor device technology, by providing optimum growth and processing conditions, and device design features required for obtaining maximum device performance. This work will be performed in collaboration with III-nitride device research group at Naval Research Laboratory (NRL). The PI has been successfully collaborating with NRL scientists, for more than 15 years, on NSF supported projects. This project offers an excellent opportunity for students for gaining hands-on experience on using state-of-the-art device growth, processing and characterization equipment in a prestigious government laboratory on an important research topic. This experience prepares students well for pursuing careers in industry and government. Both graduate and undergraduate students will participate on the proposed research.