Electronic structure of (GaAs)(m)/(Ge-2)(n)(001) superlattices with 1<=(m,n)<=20

The semiempirical tight-binding method with second-nearest-neighbor interactions has been used to investigate the electronic structure of (GaAs)(m)/(Ge-2)(n) (001) superlattices (SLs) with 1 less than or equal to(m,n) less than or equal to 20. We have found no correspondence between the calculated band structures of these (GaAs)/(Ge-2) SLs and (GaAs)(1-x)(Ge-2)(x) random alloys. The inclusion of second-nearest-neighbor interactions raised the predicted energies of the conduction band confined states while lowering that of the highest-lying interface state. For small values of m, the (GaAs)(m)/(Ge-2)(n) SLs are predicted to have indirect band gaps regardless of the valence band offset used in the calculation. For larger values of m, however, the predicted SL band gaps become direct for large values of valence band offset. (C) 1996 American Institute of Physics.