800 $^\circ$C Air-Ambient Operation of Extreme-Bandgap Al$_{x}$Ga$_{1-x}$N (x>0.6) Digital and Random-Alloy Channel HEMTs

This work demonstrates the high-temperature (room to 800 $^\circ$C) operation of thin Al$_{0.62}$Ga$_{0.38}$N digital alloy (DA) short-period superlattice (SPSL), and random alloy (RA) Al$_{0.64}$Ga$_{0.36}$N channel MOSHEMTs on sapphire. The RA devices employ a doped $n^{+}$-85%-Al barrier and a hi