Tight-binding calculation:: Electronic structure of (BeSe)n/(Si2)m superlattices

In a semiempirical sp(3)s* tight-binding scheme, bulk parameters for BeSe are determined by fitting the first-principles calculation and the detailed calculations of electronic structure of the (BeSe)(n)/(Si-2)(m) (110) superlattices are performed within a Nide range of n,m less than or equal to 20. It is found that the fundamental energy gap increases (up to 2.11 eV at the (X) over tilde point for n=m=2) with decreasing superlattice period and the Si layer plays an important role in determining the fundamental energy gap of the superlattice system due to spatial quantum confinement effects. For air reasonable values (ranging from a to 3.5 eV) of the valence-band discontinuity used in the calculation, there is an empty interface band in the thermal gap of the (BeSe)(n)/(Si-2)(m) (110) (n, m less than or equal to 20) system and the conduction band minima shift from X to Gamma along <(Gamma X)over bar> while increasing the band offset; but they never reach the Gamma point.