Low temperature AlN growth by MBE and its application in HEMTs

Low temperature growth of AlN from 470 °C down to room temperature has been studied by RF-plasma assisted molecular beam epitaxy (PAMBE). Partially amorphous AlN was achieved at growth temperatures below 250 °C. We demonstrate the application of the low temperature (LT-) AlN as an in-situ surface passivation technique for III-nitride based high electron mobility transistors (HEMTs). High 2DEG densities >2×1013 cm−2 and sheet resistance <250 Ω/□ at room temperature were first obtained for MBE grown AlN/GaN HEMT structures with thin high temperature AlN barrier, then capped with LT-AlN (<4 nm). Using this novel technique, low DC-RF dispersion with gate lag and drain lag below 2% is demonstrated for an AlN/GaN HEMT.