Negative charge trapping effects in Al₂O₃ films grown by atomic layer deposition onto thermally oxidized 4H-SiC

This letter reports on the negative charge trapping in Al₂O₃ thin films grown by atomic layer deposition onto oxidized silicon carbide (4H-SiC). The films exhibited a permittivity of 8.4, a breakdown field of 9.2 MV/cm and small hysteresis under moderate bias cycles. However, severe electron trapping inside the Al₂O₃ film (1 × 10¹² cm⁻²) occurs upon high positive bias stress (>10 V). Capacitance-voltage measurements at different temperatures and stress conditions have been used to determine an activation energy of 0.1 eV. The results provide indications on the possible nature of the trapping defects and, hence, on the strategies to improve this technology for 4H-SiC devices.