Indirect-band-gap transition in strained GaInAs/InP quantum-well structures

Using photoluminescence (PL) and time-resolved measurements, the valence-band structure of tensile strained GaInAs quantum wells has been evaluated. From temperature-dependent PL, LO-phonon-assisted transitions at energies of about 32 meV below the band gap transition were observed. In addition, a hundredfold increase in the carrier lifetime of tensile strained quantum wells compared to unstrained layers was measured. Both findings are strong indications that the maximum of the valence band in k space is shifted away from the center of the Brillouin zone in tensile strained quantum wells near a critical composition, where the lowest heavy-hole and light-hole levels cross each other, thus giving rise for indirect optical transitions as predicted by theory.