Heavy-hole intersubband transition of resonantly excited excitons in quantum wells

The exciton population in a higher subband of GaAs quantum wells, below the free carrier continuum, is studied by time-resolved luminescence spectroscopy. The lifetime of the exciton formed by an electron of the lowest subband and a heavy hole of the second subband is determined as 130 ± 20 ps, in agreement with theoretical estimations of intersubband scattering based on acoustic phonon emission. The exciton lifetime in the second heavy-hole subband is considerably longer than reported values of the recombination time in the lowest exciton state at k=0. These findings lead to novel intersubband laser concepts based on excitons