Metastable excitons in quantum wells

We present an optical (reflectance and photoluminescence) study of metastable excitons in (Formula presented) quantum-well structures. These states are associated with the type-II (Formula presented) ground-state exciton of the system. The metastable excitons are formed because the Coulomb attraction of the (Formula presented)(Formula presented) electron tends to localize the (Formula presented)(Formula presented) hole in the vicinity of the electron. This complex breaks apart as the temperature increases, and the system returns to its ground state in which the (Formula presented)(Formula presented) electron and the (Formula presented)(Formula presented) hole are segregated. © 1997 The American Physical Society.