Investigation of Ta∕Ti∕Al∕Ni∕Au ohmic contact to AlGaN∕GaN heterostructure field-effect transistor

An AlGaN∕GaN wide band-gap semiconductor with the Ta∕Ti∕Al∕Ni∕Au ohmic contact (7.5×10−7Ωcm2) was demonstrated by 700°C annealing for 1min. High-resolution electron microscopy and synchrotron-radiation x-ray diffraction showed that nitride phases were formed at the interface between the metal and the AlGaN layer. The thick formation of TaN∕TiN interfacial layers appears to be responsible for the good ohmic contact behavior in Ta∕Ti∕Al∕Ni∕Au metal scheme. The surface morphology of Ta-based contacts is superior to that of the Ti∕Al∕Ni∕Au metal scheme. The fabricated heterostructure field-effect transistor exhibited the saturation drain current density of 605mA∕mm and transconductance of 246mS∕mm.