  The energy spectrum of a two-dimensional electron gas (2DEG) interacting with
a valence-band hole is studied in the high magnetic field limit as a function
of the filling factor nu and the separation d between the electron and hole
layers. For d smaller than the magnetic length lambda, the hole binds one or
more electrons to form neutral (X) or charged (X-) excitons. The low-lying
states can be understood in terms of Laughlin-like correlations among the
constituent charged fermions (electrons and X-). For d comparable to lambda,
the electron-hole interaction is not strong enough to bind a full electron, and
fractionally charged excitons hQEn (bound states of a hole and one or more
Laughlin quasielectrons, QE) are formed. The effect of these excitonic
complexes on the photoluminescence spectrum is studied numerically for a wide
range of values of nu and d.
