We have investigated the effect of misorientated InP(001) substrates on the optical properties of InAs quantum islands (QIs) grown by molecular-beam epitaxy in the Stranski–Krastanow regime. Detailed temperature-dependent photoluminescence (PL), excitation density PL, and polarization of photoluminescence (PPL) are studied. PPL shows a high degree of linear polarization (near 40%) for the nominally oriented substrate n and for the substrate with 2° off miscut angle toward the  direction (2° F), while it is near 15% for the substrate with 2° off miscut angle towards  direction (2° B), indicating the growth of InAs quantum wires on nominal and 2° F substrates and of InAs quantum dots on 2° B substrate. These island shapes are confirmed by morphological investigations performed by atomic force microscopy. The integrated PL intensity remains very strong at room temperature, as much as 36% of that at 8 K, indicating a strong spatial localization of the carriers in the InAs QIs grown on InP(001). © 2001 American Institute of Physics.