Cooling performance of top-side polycrystalline diamond integration in RF-power N-polar GaN high-electron-mobility transistors predicted using a robust modeling platform

This study evaluates the cooling performance of top-side polycrystalline diamond (PCD) integration as an advanced thermal management strategy for N-polar GaN high-electron-mobility transistors (HEMTs) in high-power and radio-frequency (RF) electronics, using technology computer-aided design (TCAD). We constructed a robust mobility model based on well-established scattering theory and incorporated it into our device simulations, allowing reliable characterization of thermal effects and accurate projection of device performance under extreme conditions such as high temperatures and high electric fields. Large-signal power-sweep simulations of 70-nm GaN HEMTs integrated with a 500-nm PCD layer, operating at 94 GHz with applied voltages up to 20 V and bias currents of approximately 650 mA/mm, reveal a peak temperature reduction of 33%. The applied thermal management enables an increase of 39% in output power (Pout), 38% in power gain (GT), together with a 76% improvement in power-added efficiency (PAE). Our findings also reveal a superlinear increase in peak temperature with dissipated power, governed by the local electric field at the hotspot and the channel conductance. This behavior provides new physical insights into heat generation and thermal transport in GaN HEMTs.