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

Amorphous GdxGa0.4-xO0.6/Ga2O3 gate dielectric stacks have been grown onto the GaAs(001) surface by molecular beam epitaxy using high temperature effusion cells. The Ga2O3 template thickness and the Gd mole percent have been systematically varied from 73 to 0 Angstrom and from 8.8 to 22 at. % (0.088less than or equal toxless than or equal to0.22), respectively. Oxide/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 Ga2O3 template thickness of 9-11 Angstrom and a minimum Gd mole percent of 15-17 at. %. While gate oxide films with thicker Ga2O3 templates and/or lower Gd mole fraction show kinks in capacitance-voltage measurements attributed to charge trapping in the oxide, thinner Ga2O3 templates lead to strong stretch-out of capacitance-voltage curves indicating severely degraded oxide/GaAs interface properties. (C) 2003 American Institute of Physics.