Design of ohmic contacts to p-ZnSe

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Abstract
First‐principle density functional calculations are used to design improved ohmic contacts to p‐ZnSe. Two design strategies are applied: the use of a graded semiconductor epilayer with a large valence band offset, and the imposition of an interlayer to reduce the metal/p‐ZnSe Schottky barrier. In the former strategy we study BeTe because it is lattice matched to ZnSe. We find the BeTe/ZnSe valence band offset is nearly the same as the ZnTe/ZnSe offset, so that if BeTe can be sufficiently p doped, its grading with ZnSe should lead to an ohmic contact comparable to a ZnTe‐grading contact, but without the deleterious presence of misfit dislocations. For the latter strategy we consider the use of a thin As‐Si interlayer between the II‐VI material and metal. The As effects an extra microscopic dipole at the interface that lowers the Fermi level 1 eV in the II‐VI band gap, leading to greatly decreased rectification at p‐type contacts. Applying both strategies simultaneously suggests that a metal/Si‐As/BeTe/ZnSe multilayer structure would afford a nearly ideal ohmic contact to p‐ZnSe.