The quantum confined Pockels effect in InGaAs-based multi-quantum wells

Under its classical form, the envelope function theory generally used to calculate electronic properties of semiconductor heterostructures is supersymmetric >>. In particular for a structure grown along the {[}001] axis the theory predicts uncoupled heavy and light holes at the Brillouin zone center. As a consequence, optical properties should be independent of the polarization for Light propagating along the growth axis, even if an electric field is applied along this direction. Some discrepancies to this prediction may be obtained by including second order corrective terms in the k.p Hamiltonian : they have been calculated but are actually small. We observe in the contrary that InGaAs-InP multi-quantum wells show a very large dichroism which may be modified by an applied electric field : this is the quantum confined Pockels effect. We show how to complete the envelope function theory in agreement with group theory considerations and explain these observations.