Suppression and characterization of interface states at low-pressure-chemical-vapor-deposited SiN /III-nitride heterostructures

Silicon nitride (SiNx) grown by low-pressure chemical vapor deposition (LPCVD) at a reduced growth temperature (650 °C), is utilized for fabrication of GaN metal–insulator-semiconductor (MIS) power devices. An atomically sharp interface between the LPCVD-SiNx and GaN was achieved, featuring a disordered region with only a thickness of 2.5 ~ 5 Å. A fabricated LPCVD-SiNx/GaN/AlGaN/GaN MIS diode exhibits a sharp two-step capacitance–voltage behavior with small frequency dispersion of 0.4 V in the right step. The improved interface was quantified by a well-elaborated constant-capacitance deep-level transient Fourier spectroscopy (CC-DLTFS), delivering quite low density of 1.5×1013 cm-2 eV-1 at the level depth of 30 meV and about 4×1011 ~ 1.2×1012 cm-2 eV-1 at the level depth of 1 eV. Distributions of interface states can be described by a proposed physics-based decoupling function featuring an exponential law. A discrete level at the SiNx/GaN border or in the barrier layer with the level depth and the capture cross section being 0.8 eV and 5.5×10-14 cm2 respectively, can thus be detached from the interface states.