GaAs Electron Spectrum with Antisite AsGa Defect Clusters in the Semiempirical Tight-Binding Method

A computational procedure for calculating the band structure of a crystal with antisite-defect clusters is developed using a large unit-cell method. GaAs electron spectra containing clusters of more than 100 As atoms characterized by crystal point-group symmetry are calculated. The spread of energy levels in the band gap is examined. The origin of these energy levels is interpreted as being the result of splitting of energy levels of single defects.