ECCS-EPSRC: Advanced III-N Devices and Circuit Architectures for mm-Wave Future Generation Wireless Communication

无处不在的高性能通信是我们社会的支柱，不仅在个人的日常生活中发挥着越来越重要的作用，而且在设备之间的后台通信中也发挥着同样重要的作用（例如，用于移动的车辆到基础设施，工业和制造业中的过程控制和监控，全环境的虚拟化等）。因此，必须处理和通信的数据爆炸式增长需要非凡的带宽和无处不在的网络，这反过来又要求支持高性能、节能和低成本的电子产品。本提案的目标是在最关键的环节，无线功率放大器，这是必不可少的实现无处不在，高速，透明的移动通信的愿景。功率放大器是任何通信系统中最关键的元件之一，因为它们决定了系统的整体效率。基于氮化镓的hemt在高性能功率放大器方面尤其有前景，但由于器件设计和材料等因素的综合影响，目前基于氮化镓的hemt系统存在频率覆盖、效率和线性度有限的问题。在这个项目中，我们利用基于gan的晶体管设计和新型电路拓扑的变革性进步，通过协同设计，显著提高通信系统关键无线元件的效率、带宽、线性度和成本。该技术基于极化工程梯度通道GaN hemt，与传统hemt相比，线性度有了实质性的提高。通过结合对其底层器件物理（包括陷阱状态和热管理）的深入研究，我们通过优化器件设计和制造，解决了在增加频率（即Ka频段高达40 GHz）下降低GaN性能的主要影响。我们将基于我们的新型连续模式设计谐波端接放大器，使设计人员能够更广泛地选择阻抗，以实现所需的效率、线性度和输出功率特性。这将极大地增强未来通信系统的前景和潜力，例如6G无线通信。提出的技术发展将基于III-N材料和器件偏振工程的最新进展。我们将展示高线性、高效率的极化工程GaN晶体管，其性能足以消除无线功率放大器对外部线性化的需求。该计划的目标是在大信号条件下-30 dBc以下的三阶互调产品，足以在运行（而不是饱和）条件下支持50%的PAE。在这个性能水平上，相邻通道功率比（ACPR）预计足以满足监管性能要求，而无需复杂且昂贵的线性化器。我们还将展示PAE为50%、阻抗失配容忍度高的高线性宽带放大器，通过使用我们的新型连续模式放大器，为设计人员提供灵活的设计空间，以优化线性度、输出功率和效率。为了促进物理理解，深入研究极化工程GaN hemt的底层器件物理，具有纳米级分辨率。这将提供对器件和电路级的工艺、器件和存储器效应的透彻理解，这对于满足器件和电路性能目标至关重要。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。

Ubiquitous, high-performance communication is the backbone of our society, and promises to play an increasing role not only in individual's daily lives, but just as importantly in the background with communication among devices (e.g., vehicle-to- infrastructure for mobility, process control and monitoring in industrial and manufacturing, virtualization of full environments for the metaverse, among others). The resulting explosion in data that must be processed and communicated requires extraordinary bandwidth and network ubiquity, which in turn demands supporting electronics that is high performance, power efficient, and low cost. This proposal targets advancements in the most critical link, the wireless power amplifier, that is essential to realizing a vision of ubiquitous, high-speed, transparent mobile communication. Power amplifiers are among the most critical elements in any communication system as they dictate the overall efficiency of the system. GaN-based HEMTs are especially promising for high-performance power amplifiers, but current GaN-based systems suffer from limited frequency coverage, efficiency and linearity due to a combination of factors, including device design and materials issues. In this program, we leverage transformative advances in both GaN-based transistor design and novel circuit topologies to dramatically improve the efficiency, bandwidth, linearity, and cost of the key wireless elements of a communication system, through co-design. The technology is based on polarization-engineered graded channel GaN HEMTs that show a substantial improvement in linearity in comparison to conventional HEMTs. By combining with thorough investigation of their underlying device physics including trap states and thermal management, we address major effects that degrade the performance of GaN at increasing frequencies (i.e. Ka band up to 40 GHz) by optimizing device design and fabrication. We will design harmonically terminated amplifiers based on our new class of contiguous modes, that allow designers wider choice of impedances for desired characteristics of efficiency, linearity and output power. This will greatly enhance the promise and potential of future communication systems, such as 6G wireless communications.The proposed technology development will be based on recent advances in polarization engineering in III-N materials and devices. We will demonstrate high-linearity, high-efficiency polarization-engineered GaN transistors, with performance sufficient to eliminate the need for external linearization in wireless power amplifiers. This program targets third-order intermodulation products below -30 dBc under large-signal conditions, sufficient to support a PAE 50% under operational (rather than saturated) conditions. At this performance level, the adjacent channel power ratio (ACPR) is anticipated to be sufficient to meet regulatory performance mandates without complex and costly linearizers. We will also demonstrate high-linearity broadband amplifiers with PAE 50% and high tolerance to impedance mismatch, through the use of our new class of contiguous mode amplifiers to provide designers a flexible design space for optimizing linearity, output power and efficiency. To advance physical understanding, an in-depth study of the underlying device physics of polarization engineered GaN HEMTs, with nanometer scale resolution. This will provide thorough understanding of process, device and memory effects at both the device and circuit level, which is critical to meeting the device and circuit performance targets.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.