hemts made of semiconductor hetero-interfaces lacking interfacial net polarization charge, such as algaas/gaas, require positive gate voltage or appropriate donor-doping in the algaas barrier to attract the electrons towards the gate, which forms the 2d electron gas and enables conduction of electron currents. this behaviour is similar to that of commonly used field-effect transistors in the enhancement mode, and such a device is called enhancement hemt, or ehemt.