MBE-Regrown Ohmics in InAlN HEMTs With a Regrowth Interface Resistance of 0.05 $\Omega\cdot\hbox{mm}$

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 $\hbox{metal}/ \hbox{n}^{+}\hbox{-}\hbox{GaN}$ resistance ( $\sim$ 0.16 $\Omega\cdot\hbox{mm}$ ), the resistance induced by the interface between the regrown $\hbox{n}^{+}$ GaN and HEMT channel is found to be 0.05–0.075 $\Omega\cdot\hbox{mm}$ 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 $\Omega\cdot \hbox{mm}$ in GaN HEMTs.