Browsing by Subject "Surface current"
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Item Open Access Improved drain lag by reduced surface current in GaN HEMT via an ultrathin HfO2 blanket layer(IOP Publishing Ltd, 2023-04-20) Güneş, Burak; Ghobadi, Amir; Odabasi, O.; Bütün, Bayram; Özbay, EkmelThis paper reports the influence of an ultrathin 1.5nm atomic-layer-deposited HfO2 blanket layer as a gate dielectric on GaN high-electron-mobility transistors (HEMTs) grown on a 4H-SiC substrate. Transistors with a gate length of 250nm and a source-to-drain distance of 3µmwere manufactured. The proposed technique involves HfO2 deposition at 250◦C prior to the gate metallization with no additional lithography steps. This approach reduced the drain lag by 83%compared to the conventional design with no gate dielectric. The HfO2 layer suppressed the parasitic lateral conduction from the gate, reduced surface trapping, and improved gate electrostatics. The manufactured devices exhibited nearly three orders of magnitude decreased surface leakage, better turn-on behavior, and improved cut-off frequency fT linearity by 16%. High quality metal-oxide interface formation was confirmed by the conductance method. Results demonstrate that the blanket HfO2 deposition is a promising approach to improve the current dispersion characteristics and gate electrostatics of GaN HEMTs without incurring major changes to the established fabrication techniques.Item Open Access Windowed equivalence principle for open surfaces(IEEE, 2013) Takrimi, Manouchehr; Gürel, LeventWe introduce a modified current expansion scheme over open surfaces based on the equivalence theorem, which employs closed surfaces, in principle. Weighting the expansion coefficients with a suitable window function compensates for the computed field errors that occur because of the open surfaces. Numerical simulations demonstrate that the equivalent surface currents expanded with low-ordered basis functions on an open surface and weighted by suitable functions can be used to obtain the correct electromagnetic fields in a limited volume near the surface.