The effect of the proximity of a bare barrier surface on the quantum e
fficiency of underlying GaAs/Al0.3Ga0.7As and In0.13Ga0.87As/GaAs quan
tum wells (QWs) is studied by low-temperature photoluminescence. The q
uantum efficiency of the resonantly excited QWs diminishes with decrea
sing surface barrier thickness; the onset of the reduction in quantum
efficiency of the InGaAs QW occurs for a barrier that is 50 angstrom t
hicker than for the GaAs QW. A simple model of carrier tunneling to th
e surface is formulated to explain the dependence of the quantum effic
iency on surface barrier thickness and well width and height. This mod
el shows good agreement with both sets of experimental data.