Atomic and electronic structure of GaP/Si(111), GaP/Si(110), and GaP/Si(113) interfaces and superlattices studied by density functional theory

The atomic structure of GaP(111)/Si(111), GaP(110)/Si(110), and GaP(113)/Si(113) heterointerfaces was studied by ab initio calculations employing the density functional theory (DFT). Relative formation energies were computed for the interface layers allowing for atomic intermixing. The application of the electron-counting model, a construction principle used for surface reconstructions, to the case of the GaP(111)/Si(111) interfaces leads to electronic compensation at the heterovalent interfaces and to a reduction of the interface formation energy. The specific equilibrium (111) interface reconstruction can be tuned by changing the chemical potential. In particular, the GaP(111)A/Si(111) interface was found to be abrupt and uncompensated under P-rich conditions, whereas it is compensated under Ga-rich conditions. The GaP(111)B/Si(111) interface was found to be compensated. Contrary to the (111) interfaces, stoichiometric abrupt interfaces were found to be the most energetically favorable for the GaP(110)/Si(110) and the GaP(113)/Si(113) interfaces. These interfaces do not reconstruct. Although both interfaces are compensated, the GaP(113)/Si(113) superlattice exhibits a polarization field, in contrast to the (110) superlattice.