What is HEMT?

GaN (gallium nitride) has greater figures of merit than SiC, however the material is also more difficult to crystalize and process than SiC.
HEMT is a technology which is used where elements are formed only on the surface of a substrate on which GaN crystal growth is carried out.

HEMT…High Electron Mobility Transistor

Allows for formation of D-S in a significantly shorter distance than by running current across the wafer vertically, but it will remain in the ON state even if voltage is not applied between G-S. ⇒ Normally ON