Comparative study on interface and bulk charges in AlGaN/GaN metal–insulator–semiconductor heterostructures with Al2O3, AlN, and Al2O3/AlN laminated dielectrics

Abstract

In this paper, the interface and bulk charges in AlGaN/GaN metal–insulator–semiconductor (MIS) heterostructures with AlN, Al2O3, and Al2O3/AlN laminated dielectrics were studied. In situ plasma pretreatment resulted negligible interface trap states and voltage hysteresis. The fixed charge density at Al2O3/AlN (or Al2O3/barrier) interface was estimated to be 1.66 × 1013 cm−2 by using flat-band voltage shift, and the oxide bulk charge concentration was 2.86 × 1017 cm−3. The interface charge density at other interfaces were at the order of 1011 cm−2. Simulation results using the above charge density/concentration indicated that Al2O3/AlN interface fixed charges dominated the dielectric-related voltage shift in AlGaN/GaN MIS heterostructures, which caused a large voltage shift of −3 V with 10 nm Al2O3 thickness, while the flat-band voltage variety resulting from other types of charges was within 0.1 V.