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

Abstract

An equivalent oxide thickness about $1\mathrm{nm}$ for ${\mathrm{Ga}}_2{\mathrm{O}}_3\left({\mathrm{Gd}}_2{\mathrm{O}}_3\right)$ (GGO) on ${\mathrm{In}}_{0.2}{\mathrm{Ga}}_{0.8}\mathrm{As}$ has been achieved by employing a thin in situ deposited $3\mathrm{nm}$ thick ${\mathrm{Al}}_2{\mathrm{O}}_3$ protection layer. The dual gate oxide stacks of the ${\mathrm{Al}}_2{\mathrm{O}}_3∕\mathrm{GGO}$ (33, 20, 10, 8.5, and $4.5\mathrm{nm}$ )/${\mathrm{In}}_{0.2}{\mathrm{Ga}}_{0.8}\mathrm{As}∕\mathrm{Ga}\mathrm{As}$ metal-oxide-semiconductor (MOS) capacitors remain amorphous after rapid thermal annealing up to $800–850°\mathrm{C}$ , accompanied with atomically sharp smooth oxide/semiconductor interfaces. Well behaved capacitance-voltage $\left(C\text{-}V\right)$ curves of the MOS diodes have shown sharp transition from depletion to accumulation with small flatband voltage ($1.1\mathrm{V}$ for Au metal gate and $0.1\mathrm{V}$ for Al), and weak frequency dispersion (1.5%–5.4%) between 10 and $500\mathrm{kHz}$ at accumulation capacitance. Low leakage current densities [$3.1\times {10}^{-5}$ and $2.5\times {10}^{-9}\mathrm{A}∕{\mathrm{cm}}^2$ at $V=V_{\mathrm{fb}}+1\mathrm{V}$ for ${\mathrm{Al}}_2{\mathrm{O}}_3\left(3\mathrm{nm}\right)∕\mathrm{GGO}$ (4.5 and $8.5\mathrm{nm}$ )], a high dielectric constant around 14–16 of GGO for all tested thicknesses, and a low interfacial density of states $\left(D_{\mathrm{it}}\right)$ in the low ${10}^{11}{\mathrm{cm}}^{-2}{\mathrm{eV}}^{-1}$ have also been accomplished.