Measured transition from two-dimensional to three-dimensional electroabsorption as quantum-well barriers are lowered

Electric-field-dependent measurements of photocurrent spectra of $\mathrm{GaAs}-{\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ multiple quantum wells are made for $0.0013<x<\mathrm{}0.0250\mathrm{}$. Strong room-temperature exciton enhancement and quantum-confined Stark effect are observed for $x$ as low as 0.0082. Below that $x$ value behavior is more bulklike. It is at this $x$ value that theory predicts that the holes should become delocalized. This study indicates that a three-dimensional electron and a two-dimensional hole results in a two-dimensional exciton in this system.