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

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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.**