In0.53Ga0.47As/AlAs0.56Sb0.44 quantum well (QW) structures were grown on a (411)A oriented InP substrate by molecular-beam epitaxy (MBE). Photoluminescence (PL) spectra at 12 K indicated that interface flatness of a 2.4 nm thick In0.53Ga0.47As QWs on the (411)A InP substrate, which can be utilized for 1.55 mu m range all-optical-switching devices using intersubband transition (ISBT), is much superior to that of QWs simultaneously grown on a conventional (100) InP substrate over the whole range of the growth temperature (T-s=480-570 degrees C). The best value of full width at half-maximum of a PL peak (12 K) from the 2.4 nm thick In0.53Ga0.47As/AlAs0.56Sb0.44 QW grown on the (411)A InP substrate at 570 degrees C was 36 meV, which is much smaller than the best value previously reported (58 meV) for similar (100) In0.53Ga0.47As/AlAs0.56Sb0.44 QWs. This result indicates that MBE growth of In0.53Ga0.47As/AlAs0.56Sb0.44 QWs on the (411)A InP substrate significantly improves their interface flatness and 1.55 mu m range In0.53Ga0.47As/AlAs0.56Sb0.44 ISBT devices fabricated on the (41 1)A InP substrate are expected to provide much better performance. (c) 2005 American Vacuum Society.