Excitonic photoluminescence in symmetric coupled double quantum wells subject to an external electric field

The effect of an external electric field F on the excitonic photoluminescen ce (PL) spectra of a symmetric-coupled double quantum well (DQW) is investi gated both theoretically and experimentally. We show that the variational m ethod in a two-particle electron-hole wave-function approximation gives a g ood agreement with measurements of PL on a narrow DQW in a wide interval of F including flat-band regime. The experimental data are presented for a mo lecular-beam-epitaxy-grown DQW consisting of two 5-nm-wide GaAs wells, sepa rated by a 4-monolayers (ML's)-wide pure AlAs central barrier, and sandwich ed between Ga0.7Al0.3As layers. The bias voltage is applied along the growt h direction. Spatially direct and indirect excitonic transitions are identi fied, and the radius of the exciton and squeezing of the exciton in the gro wth direction are evaluated variationally. The excitonic binding energies, recombination energies, oscillator strengths, and relative intensities of t he transitions as functions of the applied field are calculated. Our analys is demonstrates that this simple model is applicable in the case of narrow DQW's, not just for a qualitative description of the PL peak positions but also for the estimation of their individual shapes and intensities. [S0163- 1829(99)01532-5].