Device Scale Heat Removal for High Power Density GaN Devices

Abstract

Gallium Nitride (GaN) High Electron Mobility Transistors (HEMTs) are thermally limited much below the electrical capability of the devices. The unique challenge of a GaN HEMT is its ultra-high heat flux at the micro-scale gate fingers. The traditional packaging and base plate level liquid cooling have limited capability and is far from the heat source, resulting in high thermal resistance from the device junction to the coolant, and ultimately limiting the RF power. We present a device-level high heat flux cooling solution with liquid micro-jet impingement within ~100 μm distance of the heat source. A preliminary demonstration of the technique on a GaN-on-Silicon device shows 50% higher heat dissipation capability, compared to the state-of-the-art pin fin base plate liquid cooling, while maintaining the device junction temperature at 150°C. If the dissipation power level is held constant at 35 W of dissipation power, the technique reduces the device junction temperature by 45°C.