As vapor pressure effects on Ga desorption during molecular beam epitaxy (MBE) were studied by photoluminescence (PL) measurements at low temperatures, and also by high-resolution transmission electron microscope measurements on undoped AlGaAs/GaAs asymmetric double-quantum-well structure. Samples were prepared on high index GaAs(n 1 1)A (n = 1, 2, 3, 4) substrates at different As pressures using two K-cells with As solid sources, and with the substrate, Ga K-cell, and Al K-cell at the same temperature. The separation of the PL peak from the wide quantum well was attributed to the dependence of quantum well width on As pressures. These separated peaks shifted toward higher energies with increasing As pressures at lower substrate temperatures.