Interface two-dimensional metallicity but lack of superconductivity in heterobonded semiconductors: ZnS/Si and GaP/Si

As a follow up to our finding that CuCl/Si superlattices exhibit metallicity at the interfaces and possibly superconductivity, we explore other semiconductor superlattices for the same properties and present here our results for ZnS/Si and GaP/Si superlattices. As found for the CuCl/Si superlattices, both the ZnS/Si and GaP/Si superlattices exhibit two-dimensional metallicity at their interfaces, as shown by their band structures, Fermi surfaces, and charge-density distributions. Furthermore, to gauge any possible superconductivity, the McMillan-Hopfield electron-phonon coupling constant, λ, is calculated using the rigid muffin-tin approximation. Electron-phonon coupling is observed mostly at the interfaces but it is not strong enough to cause superconductivity at a finite temperature as estimated using the McMillan formula for T_c. This contrasts greatly with the CuCl/Si superlattices, in which electron-phonon coupling is strong enough to indicate superconductivity.