The crystalline quality of InxAl1-xAs (x = 0.52, 0.489, 0.476) layers grown by molecular beam epitaxy (MBE) on InP substrate at 520 degrees C has been studied. From the double crystal x-ray diffraction and photoluminescence measurement, InxAl1-xAs (x = 0.52, 0.489) layers have been found to reveal high quality crystallinity and excellent optical performance. Although the In0.489Al0.511As layer of thickness of 1.116 mu m has a lattice mismatch of 0.23%, an excellent lattice coherency has been achieved. On the other hand, in the In0.476Al0.524As layer which has only a slightly larger lattice mismatch of 0.32%, stacking faults are observed. We have also observed the modulation contrast in planar view images obtained from transmission electron microscopy, which most likely arises due to the clustering of In or Al atoms. The modulation has a wavelength of about 8 nm independent of the lattice mismatch between the substrate and the epilayer.