Thermal characterisation of AlGaN/GaN HEMTs grown on silicon and sapphire substrates based on pulsed I-V measurements

High temperature pulsed measurements of AlGaN/GaN HEMTs on high resistive Si(111) substrate

“…The relative current stability in A and B classes up to 475 K can be explained by the presence of traps that are more limiting than the increases in temperature rise. In A-and B-class biasing points where V DG0 are high and comparable, we establish that access resistances and the drain current are equivalent in class B at 525 K and in class A at 325 K. In these conditions the channel temperature is considered identical for the two configurations and equal to 525 K. Then the thermal resistance is evaluated to 200 K/W knowing that the dissipated power in A class is 1 W, which is in perfect agreement with the literature [7]. No augmentation of the pinch-off voltage has been established versus temperature up to 525 K, which exclude a parallel conduction in the HR silicon substrate, and prove the high temperature behavior of this technology.…”

Modeling the effect of thin gate insulators (SiO2, SiN, Al2O3 and HfO2) on AlGaN/GaN HEMT forward characteristics grown on Si, sapphire and SiC

“…For a given MIS/GaN active layer structure, effectively, the different substrate thermal conductivity would be the main factor which establishes the channel temperature (as a function of R th which depends in turn on kappa). It is worth mentioning that, in practice, the heat flow in the hetero-structure is more complex because between the substrate and the GaN active layers there are in general a number of interfacial layers which result in additional thermal boundary resistances [46,47]. Recently, bulk GaN thermal conductivities larger than 2.6 W/cm K have been reported [48] (the theoretical value for GaN bulk kappa would be as high as 4.1 W/cm K [49]), which suggests that free-standing GaN (FS-GaN) is an interesting alternative to the excellent SiC substrates.…”

Realization of AlGaN/GaN HEMTs on Si‐on‐polySiC substrates

“…Furthermore, no clear difference is observed between these devices realized on Si-on-polySiC and devices realized on thick silicon; a slightly lower resistance change is noticed for devices realized with similar structures grown on 4H-SiC substrate due to enhanced heat transfer towards the substrate. One reason for this could be the predominant influence of the thermal resistance of the 1.8-2 µm thick GaN buffer layers [12] and/or to the Si or SiO 2 [4] films that should have to be thinner to enhance heat transfer towards the polySiC substrate.…”