In situ growth of SiN x as gate dielectric and surface passivation for AlN/GaN heterostructures by metalorganic chemical vapor deposition

SiN x grown in situ by metalorganic chemical vapor deposition (MOCVD) has shown great potential as a high-quality gate dielectric and surface passivation for AlN/GaN heterostructure transistors. In this paper, we present a thorough study on how the growth conditions affect the film quality of SiN x and correlate the observed material properties with the electrical characteristics of the heterostructures. Lowering the growth pressure and SiH 4 /NH 3 ratio can improve the SiN x /AlN interface roughness, leading to a reduced interfacial trap state density. The gate leakage current can be suppressed by increasing the resistivity of SiN x , which can be tailored with growth temperature and SiH 4 /NH 3 ratio.