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，并且不仅在个人的日常生活中，而且在设备之间的通信的背景中（例如，用于工业和制造业中的移动性、过程控制和监控的车辆到基础设施、用于虚拟实境的全环境的虚拟化等）。由此产生的必须处理和通信的数据爆炸需要非凡的带宽和网络无处不在，这反过来又要求支持高性能、高能效和低成本的电子产品。该提案的目标是在最关键的链路，无线功率放大器，这是必不可少的实现无处不在，高速，透明的移动的通信的愿景的进步。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GaN的HEMT对于高性能功率放大器尤其有希望，但是由于包括器件设计和材料问题的因素的组合，当前基于GaN的系统遭受有限的频率覆盖、效率和线性度。 在这个项目中，我们利用GaN基晶体管设计和新型电路拓扑的变革性进展，通过协同设计，大幅提高通信系统关键无线元件的效率、带宽、线性度和成本。该技术基于极化设计的渐变沟道GaN HEMT，与传统HEMT相比，该技术在线性度方面有了实质性的改善。通过结合对其底层器件物理（包括陷阱态和热管理）的深入研究，我们通过优化器件设计和制造，解决了在不断增加的频率（即Ka波段高达40 GHz）下降低GaN性能的主要影响。我们将设计基于新的连续模式类的谐波端接放大器，使设计人员能够为所需的效率、线性度和输出功率特性提供更广泛的阻抗选择。 这将极大地增强未来通信系统（如6 G无线通信）的前景和潜力。拟议的技术开发将基于III-N材料和器件的极化工程的最新进展。 我们将展示高线性度、高效率的偏振工程GaN晶体管，其性能足以消除无线功率放大器中外部线性化的需求。 该计划的目标是在大信号条件下使三阶互调产物低于-30 dBc，足以在工作（而非饱和）条件下支持PAE 50%。在此性能水平下，预期相邻信道功率比（ACPR）足以满足监管性能要求，而无需复杂且昂贵的线性化电路。 我们还将展示PAE 50%和高阻抗失配容限的高线性度宽带放大器，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。 为了推进物理理解，深入研究偏振工程GaN HEMT的底层器件物理，具有纳米级分辨率。这将提供在器件和电路层面上对工艺、器件和存储器效应的透彻理解，这对满足器件和电路性能目标至关重要。该奖项反映了NSF的法定使命，并通过使用基金会的智力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.