We used a new molecular dynamics simulation program to model the scattering of low-energy ions into the relatively open <011> axial channels of zinc-blende crystals. We also implanted 1-5 keV Si ions into GaAs/AlGaAs multiple-quantum well samples and used secondary ion mass spectrometry and photoluminescence to search for the deep ion penetration and optical damage which are characteristic of this ion channeling. Both the simulated and measured Si depth distributions have exponential tails extending at least 20 times further than the mean ion range. The photoluminescence efficiencies are severely degraded in the quantum wells which are overlapped by the observed Si profile tails. These results suggest that unintentional ion channeling is a major factor in the extensive degradation of optical and electrical properties of semiconductor surfaces which are exposed to low-energy ion bombardment during device fabrication.601316031605