1 nm equivalent oxide thickness in Ga2O3(Gd2O3)∕In0.2Ga0.8As metal-oxide-semiconductor capacitors

Abstract

An equivalent oxide thickness about 1nm for Ga2O3(Gd2O3) (GGO) on In0.2Ga0.8As has been achieved by employing a thin in situ deposited 3nm thick Al2O3 protection layer. The dual gate oxide stacks of the Al2O3∕GGO (33, 20, 10, 8.5, and 4.5nm)/In0.2Ga0.8As∕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 (1.1V for Au metal gate and 0.1V for Al), and weak frequency dispersion (1.5%–5.4%) between 10 and 500kHz at accumulation capacitance. Low leakage current densities [3.1×10−5 and 2.5×10−9A∕cm2 at V=Vfb+1V for Al2O3(3nm)∕GGO(4.5 and 8.5nm)], a high dielectric constant around 14–16 of GGO for all tested thicknesses, and a low interfacial density of states (Dit) in the low 1011cm−2eV−1 have also been accomplished.