We report a photoluminescence (PL) study of Si1-xGex/Si surface quantum wells (SFQWs). The PL peak energies are found to be affected by strain relaxation in Ge-rich SFQWs while a PL energy lowering was observed for x≤0.47 as compared to buried quantum wells capped with Si. Exciton localization in the lateral direction is suggested to be the dominant PL mechanism in SFQWs rather than perpendicular confinement effects that are expected for SFQWs. PL degradation and a spectral dominance switch over to newly developing lower energy peaks were clearly observed after prolonged air exposure. © 1997 American Institute of Physics.