1 nm equivalent oxide thickness in Ga₂O₃(Gd₂O₃)/In_0.2Ga_0.8As metal-oxide-semiconductor capacitors

An equivalent oxide thickness about 1 nm for Ga₂O₃(Gd₂O₃) (GGO) on In_0.2Ga_0.8As has been achieved by employing a thin in situ deposited 3 nm thick Al₂O₃ protection layer. The dual gate oxide stacks of the Al₂O₃/GGO (33, 20, 10, 8.5, and 4.5 nm)/In_0.2Ga_0.8As/GaAs metal-oxide-semiconductor (MOS) capacitors remain amorphous after rapid thermal annealing up to 800–850 °C, accompanied with atomically sharp smooth oxide/semiconductor interfaces. Well behaved capacitance-voltage (C-V) curves of the MOS diodes have shown sharp transition from depletion to accumulation with small flatband voltage (1.1 V for Au metal gate and 0.1 V for Al), and weak frequency dispersion (1.5%–5.4%) between 10 and 500 kHz at accumulation capacitance. Low leakage current densities [3.1×10^-5 and 2.5×10^-9 A/cm² at V=V_fb+1 V for Al₂O₃(3 nm)/GGO(4.5 and 8.5 nm)], - - a high dielectric constant around 14–16 of GGO for all tested thicknesses, and a low interfacial density of states (D_it) in the low 10¹¹ cm^-2 eV^-1 have also been accomplished.