Analysis through Modeling of Design Tradeoffs at the Transistor Level for a Beta-Ga2O3 Based Lateral Switch (Preprint)
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Air Force Research Laboratory Wright Patterson Air Force Base United States
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beta-Ga2O3 based devices show great promise for power switching applications based on metrics such as Baligas Figure of Merit FOM, exceeding Si by orders of magnitude and even exceeding emerging wide bandgap materials such as GaN and SiC. This and similar FOMs are valuable metrics to assess the promise of a material for an application. They allow materials to be compared to each other under the assumption that the ideal device can be fabricated for each material, and additionally that no other limiting factors exist. Here, an electro-thermal device model of lateral devices with realistic layouts and device properties is used to assess a number of non-idealities that will cause a material to fall short of the ideal theoretically best performance stated by the FOM. We use the model to assess the relative importance of various known performance limiters at the device level access resistance, ohmic contact resistance, etc., design considerations centered vs. offset gate, gate recess, gate field plate, dopant profile, etc., and other limiters not addressed by BFOM such as thermally limited operation. We quantify the expected improvement due to refinements in material quality, layout, channel and substrate specifications. We find that our modeled device is extremely thermally limited, such that it never really saturates at an open channel steady state bias, and additionally that thinning the backside will not fully alleviate this problem. Because of thermal limits, we find counterintuitively that maximum current is a function more of the low field mobility than the saturation velocity.