Impurity binding energies in semiconductor Fibonacci superlattices

We have calculated the density of states (DOS) of a GaAs–GaAl superlattice whose ratio between the potential energy of the impurities and the potential energy of the atoms at the lattice is a nth power of the golden mean t 1⁄4 ð1 þ ffiffi 5 p Þ=2; ðn 1⁄4 1; 2; 3;...Þ: Our theory uses Dyson’s equation together with a transfer-matrix treatment, within the tight-binding Hamiltonian model. The electronic DOS is calculated stressing the regions of frequency where the transfer function is complex, which correspond to non-localized states. q 2003 Elsevier Science Ltd. All rights reserved.