Insight into the Near-Conduction Band States at the Crystallized Interface between GaN and SiNx 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 SiN _x passivation layer grown by low-pressure chemical vapor deposition (LPCVD). A near-conduction band (NCB) state E_LP ( E_C - E_T = 60 meV) featuring a very small capture cross section of 1.5 × 10^-20 cm^-2 was detected at 70 K at the LPCVD-SiN _x/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 E_LP 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 E_LP 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.