Exciton capture by shallow quantum wells in separate confinement heterostructures

We investigate theoretically the exciton capture into shallow quantum wells in separate confinement heterostructures. The transition to the quantum well 1s, 2s, and continuum states by the emission of an LO phonon is analyzed for the material system ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs. The capture times are analytically calculated in a limiting case and numerically evaluated in the general case. The comparison of the two approaches highlights the physics of the exciton capture process. © 1996 The American Physical Society.