Magneto-photoluminescence of GaN/AlGaN quantum wells: valence band reordering and excitonic binding energies

摘要

A re-ordered valence band in GaN/AlGaN quantum wells with respect to GaNepilayers has been found as a result of the observation of an enhanced g-factorin magneto-luminescence spectra in fields up to 55 T. This has been caused by areversal of the states in the strained AlGaN barriers thus giving differentbarrier heights for the different quantum well hole states. From k.pcalculations in the quasi-cubic approximation, a change in the valence-bandordering will account for the observed values for the g-factors. We have also observed the well-width dependence of the in-plane extent of theexcitonic wavefunction from which we infer an increase in the exciton bindingenergy with the reduction of the well width in general agreement withtheoretical calculations of Bigenwald et al (phys. stat. sol. (b) 216, 371(1999)) that uses a variational approach in the envelope function formalismthat includes the effect of the electric field in the wells.