Evaluation of thermal resistance of AlGaN/GaN heterostructure on diamond substrate

Thermal assessment of AlGaN/GaN heterostructure on diamond substrate is presented. To emphasize the advantages of diamond substrate for GaN, results of test devices on GaN-on-Diamond material are compared to those on GaN-on-SiC and GaN-on-Si materials. Mesa resistors and High Electron Mobility Transistors (HEMTs) fabricated using a 0.25 µm gate length process are characterized. Infrared thermography is employed for measurement of temperature rise in the test resistors and transistors at different power dissipation conditions. Addition of a simple feature to the conventional mesa resistor is found to allow a non-destructive, on-wafer compatible and more reliable surface temperature determination using IR thermography. DC current-voltage characteristics are included to show the impact of different substrates on the electrical behavior of HEMTs. Our results clearly demonstrate a significant thermal advantage of diamond substrate compared to SiC and Si substrate for GaN HEMTs designed for closely comparable electrical performance. For the same average channel temperature rise in the identical HEMTs, we estimate that GaN-on-Diamond material used in this study allows 1.7X dissipated power of GaN-on-SiC and 3X dissipated power of GaN -on-Si.