Pseudomorphic In0.25Ga0.75As/Al0.32Ga0.68As quantum wells (QWs) with well widths (L-w) of 13, 15, 17, 19, 21, and 23 nm were grown simultaneously on the (411)A and (100) GaAs substrates at 480 degrees C by molecular beam epitaxy. The critical thickness of an InGaAs QW layer in the (411)A QW was determined by photoluminescence (PL) measurements at 11 K to be approximately 20 nm, i.e., significant increase in full width at half maximum of PL peaks was observed for L-w greater than or equal to 20 nm for (411)A QWs. This critical thickness is more than 60% larger than that (around 12 nm) of the (100) QWs,