Valence band mixing and optical emission in modulation-doped GaAs-(AlGa)As heterostructures

Unexpected optical emission spectra from electrons confined in GaAs quantum layers reveal a strong component with polarization normal to the plane of the layers. For elementary electron-hole recombination processes, this suggests surprisingly large band mixing in the ground valence subband. Effective mass theories that include conventional symmetry breaking mechanisms do not satisfactorily account for this phenomenon. The stress dependence of the spectra confirm that many body shake-up processes in the Fermi sea are important in describing emission associated with the 2D electron plasma.