Effective suppression of deep interface states and dielectric trapping in SiNx/GaN metal-insulator-semiconductor structures by a SiOxNy interfacial layer grown by plasma-enhanced atomic layer deposition

• A sharp LPCVD-SiN x /GaN interface is obtained by the PEALD-SiO x N y interfacial layer in contrast to a rough interface in the sample without the interfacial layer. • The conduction band offset (ΔE C ) between the LPCVD-SiN x dielectric and GaN increases from 2.67 to 3.77 eV by the PEALD-SiO x N y interfacial layer. • Isothermal capture transient and constant-capacitance deep-level transient spectroscopy (CC-DLTS) measurements prove the deep interface states and the electron-trapping by the bulk states in LPCVD-SiN x dielectric are effectively blocked by the PEALD-SiO x N y interfacial layer at high gate bias. A 3nm-thick SiO x N y grown by plasma-enhanced atomic layer deposition (PEALD) at 500 o C, is utilized as the interfacial layer to suppress the deep interface states and dielectric trapping in SiN x /GaN metal-insulator-semiconductor (MIS) structures. It is capable of protecting the GaN surface from decomposing during the growth of SiN x dielectric by low-pressure chemical vapor deposition (LPCVD) at a relatively high temperature of 780 o C. The SiN x /GaN interface with the PEALD-SiO x N y interfacial layer features a sharp interface, a remarkably reduced threshold voltage hysteresis (Δ V TH ) as well as suppressed interface state density. The conduction band offset (ΔE C ) between the LPCVD-SiN x dielectric and GaN increases from 2.67 to 3.77 eV by the PEALD-SiO x N y interfacial layer. It is verified by isothermal capture transient as well as constant-capacitance deep-level transient spectroscopy (CC-DLTS) measurements that, the electron-trapping by the bulk states of E C -E T ∼ 1.1 eV in the LPCVD-SiN x dielectric and the deep interface states, can be effectively blocked by the PEALD-SiO x N y interfacial layer at high gate bias. The LPCVD-SiN x / PEALD-SiO x N y bilayer could be a compelling gate dielectric for III-nitride MIS high-electron-mobility transistors (HEMTs).