Si-C alloys with direct band gaps for photoelectric application

In this paper, the novel two Si-C alloys with direct band gap of semiconductor material, namely I-43d SiC and P2/m SiC, are proposed by using density functional theory. To our knowledge, this is the first report that Si-C alloys with a stoichiometric ratio of 1:1 have direct band gaps. The Si-C alloys in the I-43d and P2/m phases have dynamical stability and mechanical stability observed through phonon spectra and elastic constants. The varies of relative enthalpies for I-43d and P2/m SiC with pressure and their stability at 50 GPa and 800 K, suggest the synthesis possibility under high temperatures and pressures. The elastic moduli (B, G, and E) of I-43d and P2/m SiC are slightly larger than the elastic muduli of C2/m-16 SiC and Si3C, C2/m-20 Si(3)C2 and Si4C. In addition, the distribution of electrons effective mass of I-43d SiC in space is equivalent. I-43d SiC has the smallest maximum electrons effective mass and holes effective mass, and the minimum value of holes effective mass appear in b axis. The two SiC alloys have direct band gaps of 0.99 and 1.44 eV, and exhibit excellent optical properties, indicating the feasibility for optoelectronic devices.