Ab initio modeling of the structural, electronic, and optical properties of AIIBIVC2V semiconductors

The structural, electronic, and optical properties of II-IV-V2 (II = Be, Mg, Zn, Cd; IV = Si, Ge, Sn; V = P, As) chalcopyrite-type ternaries have been theoretically investigated from first principles. The compounds demonstrate semiconducting behavior, with the direct-band gap ranging from about 0.2 to 2.2 eV, except for Be-containing materials, which indicate an indirect gap. The band gaps in II-IV-P-2 are always larger than corresponding ones in II-IV-As-2. All compounds are characterized by similar optical spectra with some anisotropy effects. MgGeAs2, MgSnP2, MgSnAs2, ZnSiAs2, ZnGeP2, ZnSnP2, CdSiAs2, and CdGeP2 were found to have the dipole matrix element of the first direct transition comparable with one for GaAs, that may be useful in light-emitting structures. ZnSiAs2, ZnSnAs2, and their solid solutions seem to be the most promising candidates for photovoltaic applications because of their reflectance and absorption spectra.