Measurement of the exciton binding energy in a narrow GaAs-AlxGa1-xAs quantum well by photoluminescence excitation spectroscopy

The direct measurement of the free-exciton binding energy E B in a GaAs-Al 0.25 Ga 0.75 As single quantum well is presented as a function of the well width L,. In the 20-K photoluminescence excitation spectra, 1s and 2s states of both heavy-(HH) and light-hole (LH) coupled excitons were detected, and E B was obtained from the separation of the two states. The E B for both HH and LH coupled excitons have their maximum around L z =10 monolayers (ML), and E B of LH excitons is smaller than that of HH excitons for L z ≤14 ML