New evidence of extensive valence-band mixing in GaAs quantum wells through excitation photoluminescence studies

A well-resolved split peak at the n=2 heavy-hole exciton transition observed at low temperatures in excitation spectra is characteristic of {}100-A{}-wide square GaAs quantum wells of high quality. Theoretical calculations using a multiband effective-mass approach demonstrate that the lower-energy component arises from transitions involving the n=1 light hole and n=2 electron. This strong transition, which is normally parity forbidden for symmetric square wells, becomes allowed due to valence-band mixing and along with the other transitions observed is quantitatively accounted for by the theory.