Optimized ohmic contacts for InAlGaN/GaN HEMTs

In this work, we have carried out a detailed transmission electron microscopy investigation on ohmic contacts in InAl GaN/GaN high electron mobility transistors consisting of Ti/Al/Ni/Au deposited by evaporation electron beam followed by a rapid thermal annealing at 875°C for 30s under N2 atmosphere. Subsequent to an optimized surface preparation, prior to the metal deposition, it has been possible to systematically obtain a contact resistance of 0.15-0.16 Ω.mm instead of the usual 0.5-0.6 Ω.mm. This is comparable to the state of the art results which have been published subsequent to more complex processes including molecular beam regrowth.