Electronic properties of the AlAs-GaAs (001) interface and superlattice

The tight-binding method is used to calculate the band structure and the character of the electronic states of the AlAs-GaAs (001) superlattice. The nature and value of the energy gap as a function of slab thickness is calculated. In the limit in which the thickness of the repeated superlattice slab becomes large, the system approximates a series of simple interfaces between AlAs and GaAs. This system is studied in detail, with special emphasis placed on the determination of interface states. Layer energy densities of states and charge densities per layer are found for different slab thicknesses. The electronic character of the atomic layers not directly adjacent to the interfaces closely resembles that of the bulk semiconductors in terms of anion and cation charge densities and total squared amplitude in $s$ and $p$ orbitals.