Evidence on the formation of a heavily Ge-doped layer in Pd/Ge-based ohmic contact to pseudomorphic high electron mobility transistor

Abstract

Microstructural evidence on the formation of a heavily Ge-doped layer below Pd/Ge-based ohmic contact to AlGaAs/InGaAs pseudomorphic high electron mobility transistor was obtained. The contact resistivity is decreased by two orders of magnitude as InGaAs channel is intermixed. This originates from the formation of Au2Al and Au7Ga2 compounds below the contacts during annealing, via production of group III vacancies. The vacancies play a role in producing free electrons by the incorporation of Ge atoms, resulting in intermixing of InGaAs as well as reduction of contact resistivity. (C) 1998 American Institute of Physics. [S0003-6951(98)01748-3].