Performance Enhancement of GaN Super-Lattice Castellated Field-Effect Transistors (SLCFETs) via Topside Integration of Near-Isotropic Polycrystalline Diamond

We present the performance enhancement of GaN super-lattice castellated field-effect transistors (SLCFETs) following the integration of near-isotropic polycrystalline diamond (PCD) on top as a heat spreader. This integration has led to an approximately 14% increase in saturation current (up to ~2.63 A/mm) alongside a negative threshold voltage shift, while gate leakage and off-state current still have remained nearly constant. A tensile strain, which causes a negative threshold voltage shift by increasing the 2-dimensional electron gas density, was identified in the GaN channel. A significant reduction in temperature (from ~78°C to ~47°C at 6 W/mm) was observed after PCD integration, resulting in an increase in transconductance (from 652 mS/mm to 684 mS/mm). Also, comparable pulsed IV characteristics and small-signal gains were observed in devices with and without PCD.