Excitonic lifetimes in thinInxGa1−xAs/InP quantum wells

The radiative excitonic lifetime in ${\mathrm{In}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As/InP quantum wells is studied as a function of the well width. For well thicknesses below ∼5 nm, we find an increase of the lifetime for decreasing well width, in striking contrast to the well-width dependence of the lifetime usually observed. We explain the dependence of the lifetime on well width in very thin quantum wells by a reduced transition probability caused by the penetration of the envelope wave function of the electrons into the barrier material.