Band offsets and photoluminescence thermal quenching in mid-infrared emitting GaInAsSb quantum wells with quinary AlGaInAsSb barriers

Optical transitions in Ga_0.35In_0.65As _0.32Sb_0.68/Al_0.25Ga_0.50In _0.25As_0.24Sb_0.76 quantum wells grown by molecular beam epitaxy on GaSb substrates have been detected by photoreflectance. Based on comparison with energy level calculations, the chemical conduction band offset ratio has been determined to be 78%. This translates into 65% in the real structure (i.e., after strain inclusion) which is an evidence of the expected band offset ratio modification in a quinary barrier system in favor of enhanced confinement in the valence band, when compared to similar quantum wells but with quaternary barriers. This has allowed us to explain the main photoluminescence thermal quenching mechanisms and connect the carrier activation energies with delocalization of excitons at low temperatures and the escape of holes via the confined states ladder at room temperature.