Combined exciton-electron optical processes in optical spectra of modulation doped QWs

In modulation-doped quantum well structures with electron concentration of about View the MathML source, a new resonant optical transition involving four particles (one hole and three electrons) was found in external magnetic fields in photoluminescence excitation and reflectivity spectra. This transition reveals as a narrow line between exciton and trion lines. It is identified with a combined process in which a photocreated exciton binds with an electron forming a trion and promotes for the second electron a transition to higher Landau levels.