Role of Ga2O3 template thickness and gadolinium mole fraction in GdxGa0.4−xO0.6/Ga2O3 gate dielectric stacks on GaAs

Abstract

Amorphous ${\mathrm{Gd}}_x{\mathrm{Ga}}_{\text{0.4−x}}{\mathrm{O}}_{\text{0.6}}/{\mathrm{Ga}}_2{\mathrm{O}}_3$ gate dielectric stacks have been grown onto the GaAs(001) surface by molecular beam epitaxy using high temperature effusion cells. The ${\mathrm{Ga}}_2{\mathrm{O}}_3$ template thickness and the Gd mole percent have been systematically varied from 73 to 0 Å and from 8.8 to 22 at. % $\text{(0.088⩽x⩽0.22),}$ respectively. $\mathrm{Oxide}\mathrm{/n}$ -type GaAs samples have been characterized by high-frequency capacitance–voltage measurements. Optimum gate oxide stack and oxide/GaAs interface properties are obtained with a ${\mathrm{Ga}}_2{\mathrm{O}}_3$ template thickness of 9–11 Å and a minimum Gd mole percent of 15–17 at. %. While gate oxide films with thicker ${\mathrm{Ga}}_2{\mathrm{O}}_3$ templates and/or lower Gd mole fraction show kinks in capacitance–voltage measurements attributed to charge trapping in the oxide, thinner ${\mathrm{Ga}}_2{\mathrm{O}}_3$ templates lead to strong stretch-out of capacitance–voltage curves indicating severely degraded oxide/GaAs interface properties.