Investigation of the role of isolation-feature geometry in improving the threshold-voltage adjustability and power-handling of polar III-Nitride HFETs, and physics-based modeling of the gate-current

在过去的二十年里，对宽禁带极性AlGaN/GaN异质结场效应晶体管(HFET)的研究导致了高频/大功率晶体管领域的快速增长的市场。随着这一市场份额逐渐接近10亿美元大关，用于改善晶体管的功率处理/热管理以及可靠地实现增强和耗尽操作模式(即分别具有正阈值电压和负阈值电压)的创新解决方案正在获得更突出的地位。 PI在他之前的发现拨款申请中提出了通过修改隔离特征几何结构来实现阈值电压工程的新方法，作为在同一芯片上实现增强型和耗尽型AlGaN/GaN HFET的最可行的技术，已经找到了坚实的立足点。除了PI在理论和实验基础上对理解这一现象的贡献外，其他几个团体目前也参与了这一领域非常活跃的技术和科学努力。然而，对这一现象及其能力的理解还远未完成。 在目前发现基金申请的支持下，Pi打算继续他的实验/理论参与，通过研究亚微米级的隔离特性来评估这个问题，并通过研究其他替代的III-氮化物异质结构来扩大覆盖范围。另一个将首次探索的新维度是隔离特征几何结构在限制亚微米级隔离特征实现的AlGaN/GaN HFET中自加热程度方面的作用。此外，PI将继续对这些HFET的栅漏电流进行基于物理的建模。该计划的每一个拟议研究方向都超越了PI目前的发现拨款的覆盖范围，处理了根本上的新挑战。PI的团队在他目前的NSERC发现基金的支持下，在麦吉尔大学的微制造设施中开发的微制造配方将用于实现本申请中设想的晶体管。 如果没有可靠地实现III-氮化物HFET增强/耗尽模式对的可行技术，例如这里提出的技术，这项技术就不可能完全商业化。由于这些HFET的主要市场被定义为开发用于混合动力汽车和电动汽车高压/高温应用的高效电子产品，因此提高它们的运行和可靠性可以大幅减少社会的碳足迹。这一研究项目也可以为加拿大汽车业提供优势。

Over the past two decades research on wide-bandgap polar AlGaN/GaN heterostructure field effect transistors (HFETs) has resulted in a rapidly growing market in the area of high-frequency/high-power transistors. As the share of this market is inching towards the billion-dollar mark, innovative solutions for improving the transistors’ power-handling/heat-management, and for reliable realization of both enhancement- and depletion-modes of operation (i.e. having a positive and negative threshold-voltage, respectively) are gaining a more prominent status. The novel approach of the threshold-voltage engineering via modifying the isolation-feature geometry, which was proposed by the PI in his previous Discovery grant application, has found a strong foothold as the most viable technique for realization of enhancement- and depletion-mode AlGaN/GaN HFETs on the same chip. Besides the theoretical and experimentally-based contributions of the PI to understanding this phenomenon, a few other groups are also currently involved in a very lively technological and scientific endeavor in this area. However, understanding of this phenomenon and its capacity are far from being complete. Under the support of the present Discovery grant application, PI intends to continue on his experimental/theoretical involvement in assessing this problem via looking into submicron-scale isolation-features, and to expand the scope of coverage by examining other alternative III-Nitride heterostructures. Another novel dimension that will be explored for the first time is the role of isolation-feature geometry in limiting the extent of self-heating in AlGaN/GaN HFETs realized on submicron-scale isolation-features. In addition, PI will continue to work on physics-based modeling of the gate-leakage current of these HFETs. Each of the proposed research directions of this program presents major strides beyond the coverage of PI's current Discovery grant, dealing with fundamentally new challenges. The microfabrication recipe developed by the PI’s team, with the support of his current NSERC Discovery grant, at the microfabrication facilities of McGill University, will be used in realizing the transistors envisioned in this application. Without a viable technique, such as the one proposed here, for reliable realization of enhancement-/depletion-mode pairs of III-Nitride HFET, full commercialization of this technology is not possible. Since a major market for these HFETs is defined in the area of developing high-efficiency electronics for high-voltage/high-temperature applications in hybrid and electric vehicles, improving their operation and reliability can lead to sizable reduction of the society’s carbon footprint. This research program can also provide an edge for the Canadian auto-industry.