Reduced Self-Heating in AlGaN/GaN HEMTs Using Nanocrystalline Diamond Heat-Spreading Films

Nanocrystalline diamond (NCD) thin films are deposited as a heat-spreading capping layer on AlGaN/GaN HEMT devices. Compared to a control sample, the NCD-capped HEMTs exhibited approximately 20% lower device temperature from 0.5 to 9 W/mm dc power device operation. Temperature measurements were performed by Raman thermography and verified by solving the 2-D heat equation within the device structure. NCD-capped HEMTs exhibited:  (1) improved carrier density NS, sheet resistance R_SH; (2) stable Hall mobility μH and threshold voltage VT ; and (3) degraded on-state resistance RON , contact resistance RC, transconductance Gm, and breakdown voltage V_BR .