Identification of the Ohmic-contact formation mechanism in the Au/Te/Au/GaAs system

The Ohmic-contact formation mechanism in furnace alloyed Au/Te/Au/(n-type GaAs) structures is investigated by the combined application of Mössbauer spectroscopy, x-ray diffraction, Raman scattering, and Auger-electron-spectroscopy depth profiling. A dominant shallow-donor-dopant behavior of the Te atoms (substitutional on As sites) can be questioned. The observed low-resistance conductivity is related to the presence of a (${\mathit{n}}^{+\mathrm{-}}$type ${\mathrm{Ga}}_2$ ${\mathrm{Te}}_3$)/(n-type GaAs) heterojunction. Although the possibility of some residual n-type doping of the GaAs substrate remains, evidence is adduced that, in the Ohmic-contact formation mechanism, at least an equally important role is played by a degenerate As n-type doping of the ${\mathrm{Ga}}_2$ ${\mathrm{Te}}_3$. Similar arguments are developed for the (Au-Ge)/(n-type GaAs) and Ge/Pd/(n-type GaAs) Ohmic-contact systems.