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We study exciton states in a coupled double quantum well (CDQW) semiconductor structure. Exciton levels and binding energies of direct and indirect excitons are calculated for a symmetric CDQW system with an applied electric field. The exciton states are obtained by solving the exciton effective-mass equation in the momentum space using the modified Gaussian quadrature method. Within this approach we perform realistic calculations of the exciton states by taking into account the coupling between different subband pairs and calculate optical-absorption coefficients. The calculated values of the exciton binding energy are in a good agreement with the experiment and the calculated absorption spectra qualitatively agree with the measured photoluminescence excitation spectra.

Boundary roughness scattering in disordered tunnel-coupled quantum wires in the presence of a magnetic

field is considered. The low-temperature conductance as a function of applied magnetic field is calculated for

different structure and disorder parameters using the method of the generalized S-matrix composition.We show

that despite the fact that lateral wire width fluctuations of the size of few atomic layers may significantly shift

the partial energy gap, the effect of the conductance enhancement at energies in the partial energy gap does

take place in sufficiently strong magnetic fields and small correlation length of the disorder defined as the

average distance between the neighboring discontinuities of the boundary profile. The last parameter is shown

to be particularly important for the determination of the transport properties of the system. Remarkably, we find

that in a wide range of system parameters the conductance decreases with the correlation length despite the

decreasing number of boundary discontinuities.

We investigate the effect of the boundary roughness scattering on the conductance of a disordered tunnel-coupled quantum wire in the presence of a magnetic field. It is shown that the average distance between the neighboring discontinuities of the boundary profile plays an important role in the transport properties of the system and the manifestation of the localization-delocalization effect. Present studies point out a new effect consisting in the

decrease of the conductance with the increase of the disorder correlation length.