The effect of structural disorder under bias voltage on the transmission properties of a non-interacting electron across multibarrier systems (GaAs/Alx Ga $_{1-x}$ As) is exhaustively studied by a computational model using exact Airy function formalism and the transfer-matrix technique. In ordered systems we study the effect of bias voltage on miniband structure. For disordered structures we investigate the transmission coefficient. Different types of eigenstates are obtained, those having a very low Lyapunov exponent close to the resonant energy and those with high slope in other region. Commuting resonance energy is theoretically demonstrated in this paper, the obtained values are in good agreement with the existing numerical results.

We examine numerically the effect of quasiperiodicity in the nature of the states in Fibonacci semiconductor superlattices by means of the transfer matrix formalism. We are interested in the GaAs/Alx Ga1 − x As layers, having identical thickness, where the aluminium concentration x takes, two different values. We have found that each miniband of the periodic superlattice splits in several sub-minibands, that is small minigaps appear. We demonstrate that the origin of these small inner minigaps is due to the loss of long-range quantum coherent of the electrons wave. The corresponding electronic spectrum shows a high fragment. The states having transmission coefficient close to zero in the minibands can be viewed as consisting of singular localised states.