Enhanced electrical properties of 4H-SiC/Al2O3 heterojunction by PEALD in situ NH3-plasma passivation

The carbon clusters and oxygen vacancies-induced interface traps and near-interface-oxide traps (NIOTs) at the dielectric oxide/SiC heterojunction severely degenerate the electrical properties and reliability of SiC devices. In this work, plasma-enhanced atomic layer deposition (PEALD) is performed to deposit Al2O3 dielectrics on 4H-SiC substrate to minimize the carbon cluster formation and in situ NH3-plasma pre-treatment is utilized to further improve the interfacial properties. Significantly enhanced electrical properties of the 4H-SiC/Al2O3 heterojunction is obtained with a reduced C–V hysteresis (from 0.411 V to 0.103 V) and leakage current density (from 10–3 to 10–6 A/cm2), lowered interface states (from (5.97–8.63) × 1011 to (4.10–7.56) × 1011 eV−1 cm−2) and NIOTs (from (6.15–6.82) × 1012 to (4.26–4.53) × 1011 eV−1 cm−2) and improved dielectric breakdown electric field (from 7.68 to 8.75 MV/cm). This demonstrates that in situ NH3-plasma pre-treatment associated with high-κ dielectrics is a promising technique for future high-power device applications.