Band anticrossing in highly mismatched III–V semiconductor alloys

In this paper we review the basic theoretical aspects as well as some important experimental results of the band anticrossing effects in highly electronegativity-mismatched semiconductor alloys, such as GaAs_1−xN_x and In_yGa_1−yAs_1−xN_x. The many-impurity Anderson model treated in the coherent potential approximation is applied to these semiconductor alloys, in which metallic anion atoms are partially substituted by a highly electronegative element at low concentrations. Analytical solutions of the Green's function provide dispersion relations and state broadenings for the restructured conduction bands. The solutions also lead to the physically intuitive and widely used two-level band anticrossing model. Significant experimental observations, including large bandgap reduction, great electron effective mass enhancement and unusual pressure behaviour of the bandgap, are compared with the predictions of the band anticrossing model. The band anticrossing model is extended over the entire Brillouin zone to explain the pressure behaviour of the lowest conduction band minimum in GaP_1−xN_x. Finally, we show that the band anticrossing can also account for the large bandgap bowing parameters observed in GaAs_xSb_1−x, InAs_ySb_1−y and GaP_xSb_1−x alloys.