Evaluating the High Voltage and High Frequency Capability of Future GaN-Based Diodes, MOSFETs, and Novel Photoconductive Switches

Wide bandgap semiconductor devices based on gallium nitride (GaN) offer myriads of advantages over traditional silicon (Si)-based devices for applications in power electronics. These advantages include higher voltage-handling capability with associated low conduction loss, as well as faster switching capabilities, allowing for reduced filtering components within converter topologies, thus leading to improved power density. Despite the many advantages of GaN devices, several challenges related to technological readiness level (TRL) and practical implementation have hindered their widespread adoption, particularly at high voltage. For these reasons, advanced characterization methods for GaN semiconductors are needed, so that these devices can realize their full performance <a href="http://entitlement.

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This talk will present a broad array of new characterization and modeling methodologies for future GaN diodes, MOSFETs, and novel Photoconductive Semiconductor Switches (PCSS). The presented work will include device physics simulations using finite element modeling techniques, which facilitate the design of new architectures of vertical GaN diodes that are capable of withstanding high voltages. Relative to conventional bevel-angle diodes, the proposed “hybrid edge termination” structure is much simpler, yet produces similar breakdown characteristics. It will be shown that the simulated designs can be used to fabricate and empirically characterize the static and dynamic performance of the 1.2 kV diodes. The empirically validated diode simulations inform and guide the design of high voltage GaN MOSFETs, leading to the development of scaling rules which can reasonably project the performance of future GaN devices up to 20 kV. To address potential forthcoming challenges related to Electromagnetic Interference (EMI), a novel GaN-based PCSS device is proposed and characterized. PCSS devices are optically triggered, thereby electrically decoupling the input and output ports of the device, allowing for EMI mitigation. A new “Cascaded Double Pulse Test” (C-DPT) is used to empirically characterize the dynamic performance of the PCSS device. The C-DPT consists of a low-voltage DPT, strategically positioned overtop of a high-voltage DPT. The low voltage DPT drives a UV LED, acting as the freewheeling diode to provide optical triggering to the PCSS device, which is implemented on the high-voltage DPT. This novel proof-of-concept circuit can inform the design of next-generation power converters utilizing PCSS devices. Finally, the dispersive effect of the parasitic components contained in high-frequency GaN-based circuits is evaluated. As the spectral content in GaN-based circuits is infringing on frequencies previously only observed in the RF domain, new characterization and modeling techniques are needed. This talk will demonstrate that the extended spectral content, orders of magnitude above the switching frequency, associated with GaN-based converters is causing the parasitic components of the circuit to exhibit frequency-dependence. Strategies to account for, and predict this behavior will be presented. The talk will conclude with applying learned lessons from wide bandgap semiconductors to develop a roadmap towards the design of ultra-wide bandgap devices, such as gallium oxide, or aluminum <a href="http://nitride.

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Speaker(s): Raghav Khanna,

Room: EV3.309, Bldg:
Engineering Building, Concordia University, 1515 St. Catherine W, Montreal, Quebec, Canada, H3G1M8