Carrier confinement in an ultrathin barrier GaAs/AlAs superlattice probed by capacitance–voltage measurements

The capacitance–voltage characteristics of (GaAs)m/(AlAs)n superlattices and of a GaAs/AlGaAs multiple quantum well system were used as a tool to probe the homogeneity of the studied samples. Evidences of a strong electron localization in the superlattices even with the presence of minibands were found. We interpret this result taking into account the presence of local inhomogeneities in the superlattices which causes the breakdown of the coherence of the miniband transport and therefore, give rise to the electron localization. In order to support this conclusion we numerically calculate the capacitance of the superlattices assuming a localization center near the region where electron confinement takes place and the results were found in good agreement with the measured capacitance.