Nanocrystalline Diamond for near Junction Heat Spreading in GaN Power HEMTs

Reduced performance in Gallium Nitride (GaN)-based high electron mobility transistors (HEMTs) as a result of self-heating has been well-documented. A new approach, termed "gate after diamond," is shown to improve the thermal budget of the deposition process and enable large-area diamond without degrading the gate metal. Nanocrystalline (NCD)-capped devices had 20% lower channel temperature at equivalent power dissipation. Improved electrical characteristics were observed, notably improved on-resistance and breakdown voltage, and reduced gate leakage. Further refinements to the NCD growth process have enabled deposition directly on the GaN surface. Pulsed I-V measurements indicate a comparable passivation effect to conventional SiN_x-capped devices.