In this work, a comprehensive, TCAD based design approach for mmWave (mmW) GaN HEMTs is presented. Unique trade-offs between epi-layer design and HEMT’s mmW performance are discussed. Effect of surface states on cut off frequency is modeled and presented. We have found that carrier trapping by the donor type interface states causes RF performance drift at high drain fields, which particularly leads to the non-linear behavior of mmW HEMTs at high drain bias. Moreover, we have observed that channel electrostatics, barrier layer, and UID GaN channel design govern the linearity and scaling behavior of such GaN HEMTs. To improve channel electrostatics, which improves the linearity and cut-off frequency, a partially recessed barrier under the gate is studied. A relative study of AlN/GaN HEMT and AlGaN/GaN HEMTs is performed to investigate the nonlinearity behavior. In addition, the dependence of cut-off frequency on contact resistance and lateral scaling is studied for partially-recessed barrier and conventional design for both AlN and AlGaN barrier types. The mmW performance is found to be a strong function of barrier design in the gate and recess regions. Unique design trends and physical behavior was observed for AlN and AlGaN barriers, which signifies that design guidelines derived for one epi-stack can’t be deployed to the other.

中文翻译：

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基于计算建模的器件设计，以提高 GaN HEMT 的毫米波性能和线性度

在这项工作中，提出了一种全面的、基于 TCAD 的毫米波 (mmW) GaN HEMT 设计方法。讨论了外延层设计和 HEMT 的毫米波性能之间的独特权衡。模拟并呈现表面状态对截止频率的影响。我们发现，施主型界面态的载流子俘获会导致高漏场下的 RF 性能漂移，这尤其会导致 mmW HEMT 在高漏偏压下的非线性行为。此外，我们观察到通道静电、势垒层和 UID GaN 通道设计控制此类 GaN HEMT 的线性度和缩放行为。为了改善沟道静电，从而提高线性度和截止频率，研究了栅极下方的部分凹陷势垒。对 AlN/GaN HEMT 和 AlGaN/GaN HEMT 进行了相关研究，以研究非线性行为。此外，针对部分凹入势垒和传统设计的 AlN 和 AlGaN 势垒类型，研究了截止频率对接触电阻和横向缩放的依赖性。发现 mmW 性能是栅极和凹槽区域中势垒设计的重要函数。对于 AlN 和 AlGaN 势垒，观察到了独特的设计趋势和物理行为，这意味着为一个外延堆叠导出的设计指南无法部署到另一个。发现 mmW 性能是栅极和凹槽区域中势垒设计的重要函数。对于 AlN 和 AlGaN 势垒，观察到了独特的设计趋势和物理行为，这意味着为一个外延堆叠导出的设计指南无法部署到另一个。发现 mmW 性能是栅极和凹槽区域中势垒设计的重要函数。对于 AlN 和 AlGaN 势垒，观察到了独特的设计趋势和物理行为，这意味着为一个外延堆叠导出的设计指南无法部署到另一个。