Strain fluctuations in a real [001]-oriented zinc-blende-structure surface quantum well

A theoretical study is presented of effects from strain fluctuations in a surface quantum well (SQW), which is composed of a strained zinc-blende-structure layer grown on a (001) substrate. It is found that in analogy to a zinc-blende quantum well (QW) with buried interfaces there always exist in the SQW a large fluctuating density of bulk piezoelectric charges and a high random piezoelectric field. However, in contrast to the buried QW case, roughness at a free surface of the SQW causes random fluctuations in the dilatation, which give rise to perturbing deformation potentials. The piezoelectric field and deformation potentials supply strong disorder interactions as new important scattering mechanisms for confined charge carriers in SQW’s. A comparison of their effects in a SQW and the QW under equal conditions is given.