Molecular-beam-deposited yttrium-oxide dielectrics in aluminum-gated metal–oxide–semiconductor field-effect transistors: Effective electron mobility

Abstract

We report on high effective mobilities in yttrium-oxide-based $n$ -channel metal–oxide–semiconductor field-effect transistors (MOSFETs) with aluminum gates. The yttrium oxide was grown in ultrahigh vacuum using a reactive atomic-beam-deposition system. Medium-energy ion-scattering studies indicate an oxide with an approximate composition of ${\mathrm{Y}}_{\mathrm{2}}{\mathrm{O}}_3$ on top of a thin layer of interfacial ${\mathrm{SiO}}_2.$ The thickness of this interfacial oxide as well as the effective mobility are found to be dependent on the postgrowth anneal conditions. Optimum conditions result in mobilities approaching that of ${\mathrm{SiO}}_2$ -based MOSFETs at higher fields with peak mobilities at approximately 210 ${\mathrm{cm}}^{\mathrm{2}}\mathrm{/V s}.$