Biexcitonic binding energies in the transition regime from three- to two-dimensional semiconductors

We study the dependence of the binding energies of excitonic molecules on the confinement in semiconductor quantum wells. A set of symmetrically strained (GaIn)As/Ga(PAs) quantum wells with different well depths and equal well widths is investigated with transient degenerate four-wave mixing. The ratio of biexcitonic to excitonic binding energy increases with stronger confinement. This experimental result is discussed in detail in the framework of recent theoretical predictions and experimental results.