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

Under its classical form, the envelope function theory generally used to ca lculate electronic properties of semiconductor heterostructures is << super symmetric >>. In particular for a structure grown along the [001] axis the theory predicts uncoupled heavy and light holes at the Brillouin zone cente r. As a consequence, optical properties should be independent of the polari zation for Light propagating along the growth axis, even if an electric fie ld is applied along this direction. Some discrepancies to this prediction m ay be obtained by including second order corrective terms in the k.p Hamilt onian : they have been calculated but are actually small. We observe in the contrary that InGaAs-InP multi-quantum wells show a very large dichroism w hich may be modified by an applied electric field : this is the quantum con fined Pockels effect. We show how to complete the envelope function theory in agreement with group theory considerations and explain these observation s.