TIME-RESOLVED PHOTOLUMINESCENCE STUDY OF GAINAS ALGAINAS SUPERLATTICES/

We present results of time-resolved photoluminescence experiments perf ormed at 77 K on a GaInAs/AlGaInAs superlattice grown by molecular bea m epitaxy and lattice matched to an InP substrate. The superlattice is the intrinsic part of a p-i-n diode. Photoluminescence spectra, recon structed at various delay times between 5 ps and 100 ps after the lase r pulse, show lines associated to the Is and 2s heavy-hole exciton sta tes and to the free carrier recombination. This result provides a dire ct determination of the binding energy of the heavy-hole exciton which is shown to be equal to 15 meV. Such a large value of the Rydberg is due to the fluctuations of composition which cause the heavy-hole exci ton to be localized within a single well. The spectra also exhibit a s houlder which corresponds to the electron-to-light-hole transition. Th e 2s heavy-hole-exciton transition is coupled to the latter by an LO p honon. Finally a transition 21 meV below the Is heavy-hole-exciton ene rgy is related to Be residual impurities. (C) 1998 Academic Press.