MBE-Regrown Ohmics in InAlN HEMTs With a Regrowth Interface Resistance of 0.05 Ω . mm

Nonalloyed ohmic contacts regrown by molecular beam epitaxy were made on InAlN/AlN/GaN/SiC high-electron-mobility transistors ( HEMTs). Transmission-line-method measurements were carried out from 4 K to 350 K. Although the total contact resistance is dominated by the metal/n(+)-GaN resistance (similar to 0.16 Omega . mm), the resistance induced by the interface between the regrown n(+) GaN and HEMT channel is found to be 0.05-0.075 Omega . mm over the entire temperature window, indicating a minimal barrier for electron flow at the as-regrown interface. The quantum contact resistance theory suggests that the interface resistance can be further reduced to be < 0.02 Omega . mm in GaN HEMTs.