Low-pressure, metal-organic vapor-phase epitaxy (MOVPE) was used to grow AlN/GaN metal-insulator-semiconductor (MIS) heterostructures with AlN thickness between 3 nm and 30 nm. The Hall mobility was found to decrease with increasing AlN thickness, with optimal mobility measured at 5-nm AlN. By decreasing the ammonia flow during AlN growth (lower V/III ratio), surface and interface quality were greatly improved with a corresponding improvement in electrical properties. For the optimal V/III ratio, room-temperature (RT) mobility and sheet charge were 891 cm2/Vs and 2.15 × 1013 cm-2, respectively. The best RT mobility, for both optimal V/III and thickness, was 1015 cm2/Vs with a sheet charge of 1.1 × 1013 cm-2.
