Asymmetric line-shape of optical transitions in multiple quantum wells

In this work we present a study of the line-shape of the interband optical transitions in several InxGa1-x As /GaAs MQWs with 4-6 periods. We predict by calculations and confirm experimentally that the line-shapes in such structures are asymmetric. The energy levels and the envelope wavefunctions of the sub-levels have been calculated using the effective mass approximation. For optical transitions between confined states symmetric line-shapes are predicted by the overlap integrals (OI) only for the forbidden (Δn ≠ 0) transitions, while the OI are observed to enhance on the high-energy side of the allowed (Δn = O) transitions. The opposite asymmetry trend is observed for OIs of spatially indirect transitions involving light holes (e1-lh1). For less confined states the asymmetry increases and a variety of line-shapes is expected for transitions involving above-barrier states. In the case of large enough subband splittings the calculated trends have been experimentally confirmed by the observed asymmetric line-shapes from photoluminescence excitation spectroscopy in a series of InxGa1-xAs/GaAs MQWs at T= 11 K. © 1998 Elsevier Science B.V. All rights reserved.