Sheet carrier density enhancement by Si3N4 passivation on nonpolar a-plane (112¯) sapphire grown AlGaN∕GaN heterostructures

The AlGaN∕GaN heterostructures (HSs) with high two dimensional electron gas mobility (1070cm2∕Vs) were grown on nonpolar a-plane (112¯0) sapphire substrate by metal organic chemical vapor deposition. High crystalline quality (reduced screw, edge, and mixed dislocations) with small root mean square surface roughness and small peak-valley distance values were observed in a-plane sapphire grown AlGaN∕GaN HSs. Hexagonal-GaN phase was also observed on a-plane sapphire grown AlGaN∕GaN HSs. An average increase of ns up to 22% for a plane and 26% for c plane were found after Si3N4 passivation. The product of ns and μH also increases for both a-plane (19%) and c-plane (28%) sapphire grown AlGaN∕GaN HSs in a wide range of measurement temperature (87–400K). The enhancement of sheet carrier density by Si3N4 passivation for nonpolar (112¯0) sapphire grown AlGaN∕GaN HSs is a useful result for the design of future GaN high-electron-mobility transistors.