Breakdown of rotational symmetry at semiconductor interfaces: A microscopic description of valence subband mixing

The recently discovered in-plane optical anisotropy of [001]-grown quantum wells offers a new theoretical and experimental insight into the electronic properties of semiconductor interfaces. We first discuss the coupling of X and Y valence bands due to the breakdown of rotation inversion symmetry at a semiconductor hetero-interface, with special attention to its dependence on effective parameters such as the valence band offset. The intracell loc alization of Bloch functions is explained from simple theoretical arguments and evaluated numerically from a pseudo-potential microscopic model. The r ole of envelope functions is then considered, and we discuss the specific c ase of non-common atom interfaces. Experimental results and applications to interface characterization are presented. These calculations give a micros copic justification, and establish the limits of the heuristic "H-BF" model .