Detection of large in-plane spin-dephasing anisotropy in [1Â 0Â 0]-grown GaAs/AlGaAs quantum wells

► Large in-plane spin dephasing anisotropy has been observed in highly asymmetric GaAs quantum wells. ► In-plane spin dephasing anisotropy reduced with increase in photo-excited electron density. ► Measured degree of in-plane spin dephasing anisotropy also qualitatively agrees with the designed degree of structural inversion asymmetry. ► It is discussed that the Dresselhaus spin-orbit coupling dominates Rashba one for all samples.