Insulating layers of polycrystalline GaAsS compounds grown by reactive plasma sputtering

Abstract

GaAsS ternary compounds are obtained from reactive radio-frequency cathodic sputtering of a monocrystalline gallium arsenide target in an argon and sulfurous hydrogen plasma. Thin films deposited on temperature controlled molybdenum substrates enable us to obtain a sandwich structure: Au/GaAsS/Mo. Electrical (current–voltage) characterizations show a change, with sulfur concentration, in the compound behavior, from a highly doped semiconductor to a heavily insulating material. Maximum serial resistivity (3×10 14 Ω cm) is attained with a sulfur concentration of 50% (arsenic concentration being nearly 0%) and a typical space-charge-limited (SCL) conduction is obtained. We determine dielectric permitivity from capacitative measurements. This material presents insulating properties (varying with sulfur concentration) equivalent to those of SiO 2 compounds. Moreover epitaxial layers can be grown on GaAs substrate, which will lead to applications in GaAs technologies as an insulator or an interface (depending on lattice parameter).