Delta-doped ohmic contacts to n-GaAs

A new type of nonalloyed ohmic contact to GaAs is realized by molecular beam epitaxy. The ohmic characteristic of the metal-semiconductor junction is obtained by placing a highly δ-doped donor layer a few lattice constants away from the metal-semiconductor interface of the contact and thus keeping the tunneling barrier extremely thin. The current-voltage characteristic of the δ-doped contacts is strictly linear. The measured contact resistance is in the 10−6 Ω cm2 range. Theoretical analysis of the tunneling current through the triangular barrier predicts contact resistances in the range 10−7–10−9 Ω cm2. In spite of the high doping concentration (≂1021 cm−3) the surface morphology of the sample shows no degradation.