Space group symmetry of the conduction band minimum in very short period GaAs AlAs superlattices

In a perfect (GaAs)_m(AlAs)_n type-II superlattice the symmetry of the conduction band states, and therefore the band mixing, depends on whether m, n or (m+n) are odd or even. We have investigated the symmetry of the conduction band minima in very short-period superlattices (m≤n≤4) by time resolved photoluminescence under applied uniaxial stress, and find that selection rules that depend on space group symmetry through k-conservation are well obeyed, but parity with respect to space inversion is apparently not a good quantum number in our samples.