Enhancement of optical absorption induced by disorder in three‐dimensional random superlattices

The effect of disorder on the optical absorption of the realistic random superlattice has been investigated based on a three‐dimensional tight‐binding Hamiltonian. It is found that the absorption intensity close to the band edge of the random superlattice is considerably enhanced, which can be explained by optical matrix elements of the relevant eigenfunctions localized strongly over 2–4 monolayers. An energy‐level crossing behavior at the conduction‐band bottom is also obtained.