GaAs1−xPx/AlyGa1−yAs (x=0.07–0.15,y=0.3) strained‐layer quantum wells have been grown on GaAs‐(111)B substrates by low‐pressure metalorganic vapor phase epitaxy and characterized by photoluminescence (PL) spectroscopy. Evident energy blue shifts of the excitonic transition peaks (some of them as large as 33 meV) were achieved by increasing the excitation power during the PL measurement. The large optical nonlinearity mainly due to the strain‐induced piezoelectric field screened by the photoexcited carriers, is comparable to, or larger than, the reported values for a self‐electro‐optical effect device or other (111)‐oriented strained‐layer quantum well structures which are composed of InGaAs/GaAs or GaAs/GaAsP. This fact indicates that our (111)‐GaAsP/AlGaAs strained‐layer quantum well is a good candidate for making optoelectronic devices like optical switches and modulators. ©1995 American Institute of Physics.