A study of Ge/GaAs interfaces grown by molecular beam epitaxy

Abstract

Ohmic contacts to n-GaAs using a Ge/GaAs heterojunction have been developed. Ge layers with free-electron concentrations above 1×1020 cm−3 have been grown on GaAs by molecular beam epitaxy (MBE). Gold evaporated on such structures forms tunnel contacts through the Ge to the GaAs. The lower barrier height of metals on Ge compared to GaAs and the small barrier at the Ge/GaAs heterojunction facilitates the formation of contacts with specific contact resistances below 10−7 Ω cm2.