CAREER: A multi-scale and hierarchical computational framework to model III-nitride devices operating in the near-terahertz regime

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Wide and ultrawide bandgap III-nitride semiconductors have the foundational capability to meet the power and frequency requirements of near-terahertz communication systems with bandwidths exceeding 100 gigahertz. III-nitrides are also well positioned to be used in extreme environments, from the cryogenic limit to high temperatures. However, the demonstrated performance of III-nitride devices today is still below theoretical expectations, and the promise of III-nitrides for near-terahertz applications remains unfulfilled. Still experimental advances in isolation of theoretical advances are unlikely to change this existing landscape. To tackle this challenge, in this research, we will create a multi-scale and hierarchical computational framework that will provide a high fidelity insight into the underlying physics of III-nitride devices at different length-, time-, and temperature-scales. These fundamental insights are crucial for identifying material- and device-level advances that will push the bounds of III-nitrides’ based wireless technologies, be it for commercial wireless communication or scientific investigations in extreme environments. This research will have a far reaching impact in areas like healthcare, energy, transportation, space programs, and social and educational advancements. The models developed here will be fully open-source and available to researchers world-wide, amplifying the scale and impact of this research. We will inaugurate an afterschool semiconductors-focused summer camp for middle school students and collaborate with the Inclusivity, Diversity, Equity and Access Institute at the University to recruit low-income and minority students in the department and in our research lab. Web-based learning library on semiconductor physics will be developed to encourage students to think creatively about the possibilities of semiconductors in next-generation electronic systems. The success of this research, outreach and educational plan holds promise to result in decades of productive fundamental knowledge, contribute to translation into important near-terahertz technologies, and motivate the participation and retention of a diverse community of electrical engineers, materials scientists, and physicists.Modeling and simulation tools are the cornerstones of the physics-based and application-driven device and circuit design. Because III-nitride devices are intended for use in high-field and high-frequency applications, current models that neglect Maxwell’s full-wave effects and full-band physics fail at guiding experiments for technology optimization and cannot fully explore the materials-to-circuit design space, which is highly desirable for meeting target performance metrics. Thus, it is safe to say that a fundamental rethinking of computational methodologies for III-nitride devices will be a game-changer for a myriad of near-terahertz applications that can address some of the biggest challenges of current and future times. In this research, we will create a multi-scale computational framework that combines first-principles calculations through numerical transport simulations to a compact circuit model. This framework will identify new theoretical means to interrogate and control the high-frequency and off-equilibrium physics of the near-terahertz III-nitride devices. Salient features of this computational framework include full electronic bandstructure, hot-electron effects, self-heating, quantum-mechanical scattering, charge trapping, low-temperature physics, and full-wave electromagnetics. Because the numerical framework will be complemented with a SPICE-compatible and experimentally validated compact model, the proposed research will enable large-scale circuit simulations and systems design. The outcomes of this research will benefit many stake holders, from material scientists to circuit designers, and enable cross-disciplinary interactions that will set the global stage for multi-generational research in wide and ultrawide bandgap semiconductors.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.