Vacancy effects on optical gap in GaAs in the presence of spin orbit interaction

We calculate the band structure of the Ga As in the presence of vacancy, in the effective mass approximation (EMA) by using virtual crystal approximation based on an 8-band kp formalism. For the calculations shown, the Hamiltonian constructed by Trebin et al. has been implemented. This 8-band kp Hamiltonian is constructed solely on group theory arguments and, when applied correctly, guarantees the inclusion of all matrix elements compatible with the Td symmetry group of the zincblendes up to the desired order in the electron wave vector k.Finally we have calculated energy gap in various wave vector K versus vacancy percent . It is shown that by increasing vacancy percent the band gap energy is decreased. So we can control optical properties of this mater by changing vacancy percent.