Electron-hole systems in narrow quantum wells: excitonic complexes and photoluminescence

The energy and photoluminescence (PL) spectra of a two-dimensional electron gas (2DEG) interacting with a valence-band hole are studied in the high-ma gnetic-field limit as a function of the filling factor v and the separation d between the electron and hole layers. For d smaller than the magnetic le ngth lambda, the hole binds one or more electrons to form neutral (X-0) or charged (X-) excitons, and PL probes the lifetime and binding energies of t hese complexes rather than the original correlations of the 2DEG. The low-l ying states can be understood in terms of Laughlin-type correlations among the constituent negatively charged Fermions (electrons and X(-,)s). For d, large compared to lambda, the electron-hole interaction is not strong enoug h to bind a full electron, and fractionally charged excitons hQE(n) (bound states of the hole and one or more Laughlin quasielectrons) are formed. The PL selection rule associated with rotational invariance (conservation of L ) is only weakly violated in the interacting plasma, and the position and o scillator strengths of PL lines can be predicted and compared with numerica l calculations. (C) 2001 Elsevier Science B.V. All rights reserved.