Abstract
We have used photoluminescence excitation (PLE) spectroscopy to study the evolution of the electronic states, and associated optical transitions, as the number of wells is increased from 2 to 5 to 20 in the strained (In,Ga)As-GaAs quantum-well system. The indium fraction in the wells was nominally 0.12. The PLE spectra of the two-well and five-well samples show strong Δn=0 exciton transitions and further features associated with transitions from confined states to continuum states. When a superlattice (SL) is formed, in the 20-well sample, we see momentum-conserving optical transitions at the mini-Brillouin-zone center and edge. We have also identified transitions associated with critical points in the SL band structure. One of these is a Δn=0 exciton resonance below the saddle point while the other is a Δn≠0 exciton which has become allowed due to momentum mixing of the light- and heavy-hole bands in the plane perpendicular to the growth direction.
- Received 19 March 1990
DOI:https://doi.org/10.1103/PhysRevB.42.3024
©1990 American Physical Society