Band structure of semiconductor superlattices

A theory of the band structure of semiconductor superlattices has been developed for both the direct-band-gap and indirect-band-gap barrier layers taking into account the multivalley and nonparabolic band structure of the materials forming the superlattice. For direct-band-gap barrier layers the nonparabolicity in the band structure may alter the electronic energy levels measured from the bottom of the potential wells by as much as 26%. On the other hand for indirect-band-gap barrier layers the alteration due to the nonparabolicity is about 14%. It is also found that even for indirect-band-gap barrier layers the band structure is mainly determined by the states corresponding to the direct-gap minimum. Energy levels calculated on the basis of the theory presented are also found to agree with those obtained in recent experiments with double-barrier heterostructures.