Device-level Transient Cooling of β-Ga2O3 MOSFETs

β-phase gallium oxide (β-Ga2O3) has garnered considerable attention due to its large critical electric field strength and the availability of low cost/high quality melt-grown substrates, both of which are advantages over silicon carbide (SiC) and gallium nitride (GaN) in terms of the development radio frequency (RF) and power switching devices. However, because of the low thermal conductivity of β-Ga2O3, thermal management strategies at the device-level are required to accomplish the targeted high power operation. Recent package- and system-level thermal management studies have shown that design solutions based on steady-state operation could lead to ineffective cooling performance under transient thermal loading conditions, and result in an overdesigned cooling system. For these reasons, we performed a comparative study of the thermal dynamics of β-Ga2O3 and GaN based transistor devices, which sheds light on the design of device-level transient cooling solutions for β-Ga2O3 metal-oxide-semiconductor field-effect transistors (MOSFETs). Results show that replacing the host β-Ga2O3 substrate with a high thermal conductivity material, similar to device-level thermal management solutions established for GaN devices, is effective in terms of heat extraction from the device active region under direct current (DC) operating conditions, but not under high frequency power dissipating conditions beyond the ~10² kHz range. In order to cool lateral β-Ga2O3 MOSFETs under transient pulse-powered conditions, additional topside heat extraction via a high thermal conductivity passivation overlayer is necessary.