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.