Improved interface abruptness was achieved in pseudomorphic InxGa1-xAs/Al0.34Ga0.66As quantum wells (QWs) (x similar or equal to 0.2) with extremely flat interfaces over a wafer-size area [(411)A superflat interfaces] grown on (411)A GaAs substrates by decreasing the substrate temperature T-s under a low V/III ratio during molecular beam epitaxy (MBE). Significant redshifts of low-temperature (12 K) photoluminescence (PL) peaks were observed for the (411)A and simultaneously grown (100) QWs with decreasing T-s because of the improved interface abruptness resulting from suppressed surface segregation of In atoms during MBE. Full widths at half maximum (FWHMs) of the PL peaks from the (411)A QWs grown at T-s = 450-540 degreesC under the low V/III [As-4/(Ga+In)] pressure ratio of 10 showed almost no dependence on T-s and were 20%-30% smaller than the best PL FWHMs of the corresponding (100) QWs of this study, indicating that the (411)A InGaAs/AlGaAs superflat interfaces can be successfully formed even for the low T-s of 450 degreesC.