Electronic and optical properties of alkali halides KBr/RbCl superlattices

Electronic and optical properties of alkali-halides NaCl-structure KBr/RbCl superlattices are calculated by the first-principles and variational methods. It is shown that KBr/RbCl is a type-superlattice whose band offsets are independent of the interface orientation because of small covalency between constituents. Due to the sizable compensation between the confinement and binding energies of exciton, the excitonic band-gap energy shows a small increase with decreasing the quantum-well layerthickness, which is in good agreement with experimental results. Higher-energy absorption spectra of these systems are also discussed.