Insight into the Near-Conduction Band States at the Crystallized Interface between GaN and SiN_x Grown by Low-Pressure Chemical Vapor Deposition

Constant-capacitance deep-level transient Fourier spectroscopy is utilized to characterize the interface between a GaN epitaxial layer and a SiNx passivation layer grown by low-pressure chemical vapor deposition (LPCVD). A near-conduction band (NCB) state ELP (EC – ET = 60 meV) featuring a very small capture cross section of 1.5 × 10–20 cm–2 was detected at 70 K at the LPCVD-SiNx/GaN interface. A partially crystallized Si2N2O thin layer was detected at the interface by high-resolution transmission electron microscopy. Based on first-principles calculations of crystallized Si2N2O/GaN slabs, it was confirmed that the NCB state ELP mainly originates from the strong interactions between the dangling bonds of gallium and its vicinal atoms near the interface. The partially crystallized Si2N2O interfacial layer might also give rise to the very small capture cross section of the ELP owing to the smaller lattice mismatch between the Si2N2O and GaN epitaxial layer and a larger mean free path of the electron in the crystallized portion compared with an amorphous interfacial layer.