An AlN/Al0.85Ga0.15N high electron mobility transistor with a regrown ohmic contact

The performance and efficiency of power devices depends on both high breakdown voltage and low on-state resistance. For semiconductor devices, the critical electric field (E
_C
) affecting breakdown scales approximately as E
_g
²⁵
[1], making the wide bandgap semiconductor materials logical candidates for high voltage power electronics devices. In particular, AlGaN alloys approaching AlN with its 6.2 eV bandgap have an estimated E
_C
approaching 5x that of GaN. This factor makes AlN/AlGaN high election mobility transistors (HEMTs) extremely interesting as candidate power electronic devices. Until now, such devices have been hampered, ostensibly due to the difficulty of making Ohmic contacts to AlGaN alloys with high Al composition. With the use of an AlN barrier etch and regrowth procedure for Ohmic contact formation, we are now able to report on an AlN/AlGaN HEMT with 85% Al.