Stress-induced charge trapping and electrical properties of atomic-layer-deposited HfAlO/Ga₂O₃ metal–oxide–semiconductor capacitors

Electrical properties and trapping characteristics of an atomic layer deposited Al-rich HfAlO/β-Ga₂O₃ capacitor were evaluated via constant-voltage stress (CVS), capacitance–voltage (C–V), and current–voltage (I–V) measurements. The magnitude of the stress-induced charge trapping increases with increasing voltage and time. The effective charges (N _eff) including the 'border' traps located in near-interface oxide, interface traps (D _it) of HfAlO/β-Ga₂O₃ interface, and fixed charges contribute significantly to the observed charge trapping, and it is found that interface traps contribute more under a large stress bias, compared with 'border' traps. In addition, the effective charge density is increased with stress time, implying that the contribution of negative sheet charges during the CVS process might not be negligible. Measurements of oxide permittivity (10.74), interface state density (D _it ∼ 1  ×  10¹² eV⁻¹ cm⁻²), and gate leakage current (1.18  ×  10⁻⁵ A cm⁻² at  +10 V) have been extracted, suggesting the great electrical properties of Al-rich HfAlO/β-Ga₂O₃ MOSCAP. According to the above analysis, Al-rich HfAlO is an attractive candidate for normally off Ga₂O₃ transistors. (paper)