Ohmic Contracts to Gallium Aluminum Arsenide for High Temperature Applications

摘要

A method of modifying the Gallium Arsenides (100) interface Fermi level position (EF) has been investigated. For tunnel ohmic contacts the contact resistance depends exponentially on the energy difference between the conduction band minimum and EF; thus, stable contacts with small values of this energy difference (large values of EF) could be important in designing nonalloyed ohmic contacts. Very thin (approx. 10A) epitaxial layers of Gallium that incorporate Arsenic have been found to produce exceptionally large values of EF, 1.0-1.2 eV relative to the valence band maximum (as determined by x-ray photoelectron spectroscopy). Thick model contacts that include layered structures of Au, Ge, and Ni in various combinations have been used to establish conditions under which these large EF values can be preserved (as determined by current-voltage measurements). The results question the usual assumption of a near mid-gap EiF position for the widely used alloyed AuGeNi ohmic contact and offer an alternative explanation for the mechanism of ohmic contact formation.