High performance InAlN/GaN/Si high electron mobility transistor using microwave ohmic annealing technique

In this study, a high-performance InAlN/GaN high electron mobility transistor (HEMT) was fabricated using low-temperature microwave annealing (MWA) as the ohmic metal alloy process for the first time. Ni-Al alloy aggregation is significant for InAlN devices because of the high Al fraction in InAlN layer. Furthermore, the indium segregation and out-diffusion of the InAlN barrier layer resulted in lower drain current and the formation of extra trap centers. Compared with traditional rapid thermal annealing with a high-temperature process window, MWA results in simultaneously superior ohmic contact and wafer sheet resistances because of the superior surface morphology of the ohmic metal alloy in the MWA device. Moreover, the heterostructure interfacial quality of two-dimensional electron gas density can be maintained through low-temperature MWA, as indicated by reciprocal space map measurements. Furthermore, Baliga's figure-of-merit calculation indicated that the MWA-InAlN HEMT had superior DC characteristics, providing improved device radiofrequency bandwidth and output power density performance.