Delta-Doped Ohmic Contacts to n-GaAs.

A new type of non-alloyed ohmic contact to GaAs is realized by molecular-beam epitaxy. The ohmic characteristic of the metal-semiconductor junction is obtained by placing a highly delta-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 delta-doped contacts is strictly linear. The measured contact resistance is in the 10(-6)omega cm(2) range. Theoretical analysis of the tunneling current through the triangular barrier predict contact resistances in the range of 10(-7) to 10(-9)omega cm(2). In spite of the high doping concentration (~10(21)cm(-3) the surface morphology of the sample shows no degradation.