Optical properties of a strained GaAs0.64Sb0.36/GaAs and a strain-compensated GaAs0.64Sb0.36/GaAs/GaAs0.79P0.21 triple quantum well (TQW) structures were investigated by photoluminescence (PL), photoreflectance (PR) and surface photovoltage spectroscopy (SPS). The samples were grown on GaAs(100) substrates by a horizontal metal-organic vapor phase epitaxy (MOVPE) system. For GaAs0.64Sb0.36/GaAs TQW, a large blueshift of the peak position of PL feature at low temperature with increasing excitation power density and only a very weak PR feature observed in the vicinity of fundamental transitions and were attributed to a weakly type-II heterojunction formed between GaAs0.64Sb0.36 and GaAs. On the other hand, the PR and SPS spectra of GaAs0.64Sb0.36/GaAs/GaAs0.79P0.21 TQW showed a series of intersubband originated transition features, which is a typical characteristic of type-I QW structure. The results revealed that the energy band of QW structures is significantly influenced by the inserted tensile GaAsP layers, which changes the weakly type-II to a type-I structure. The strain-compensated GaAs0.64Sb0.36/GaAs/GaAs0.79P0.21 TQW has a larger overlap integral and hence a higher transition probability, providing a possibility for fabricating high efficiency near infrared laser diodes. (C) 2012 Elsevier B.V. All rights reserved.