GaN high electron mobility transistors (HEMTs) with self-upward-polarized AlScN gate dielectrics toward enhancement-mode operation

Abstract

Abstract A threshold voltage ( V th ) shifting method for GaN high electron mobility transistors using self-upward polarized Al 1- x Sc x N gate dielectrics was proposed. The direction of the spontaneous polarization was controlled by the insertion of an Al 2 O 3 layer between the Al 1- x Sc x N and the AlGaN layers. A V th shift of 8 V was found by changing the direction of the polarization. The thickness scaling in the Al 1- x Sc x N layer from 40 to 30 nm showed a linear relationship to the V th , revealing to retain a high spontaneous polarization. A high positive V th for enhancement-mode (E-mode) operation is feasible with the method in combination with a recess process.