Magnetophonon resonance in photoluminescence excitation spectra of magnetoexcitons in GaAs/Al0.3Ga0.7As superlattice

A strong increase in the intensity of the peaks of excited magnetoexciton ( ME) states in the photoluminescence excitation (PLE) spectra recorded for t he ground heavy-hole magnetoexcitons (of the 1sHH type) has been found in a GaAs/Al0.3Ga0.7As superlattice in strong magnetic field B applied normal t o the sample layers. While varying B, the intensities of the PLE peaks have been measured as functions of energy separation Delta E between excited ME peaks and the ground state of the system. The resonance profiles have been found to have maxima at Delta E-max close to the energy of the GaAs LO pho non. However, the value of Delta E-max depends on quantum numbers of the ex cited ME state. The revealed very low quantum efficiency of the investigate d sample allows us to ascribe the observed resonance to the enhancement of the nonradiative magnetoexciton relaxation rate arising due to LO-phonon em ission. The presented theoretical model, being in a good agreement with exp erimental observations, provides a method to extract 1sHH magnetoexciton "i n-plane" dispersion from the dependence of Delta E-max on the excited ME st ate quantum numbers.