A nonradiative dark region along a surface ripple is observed in optically and electrically excited GaP LPE layers. The region originates from the substrate interface and terminates at the ridge of the surface ripple. It is clearly distinguishable from the known one caused by dislocation in its features. Thep‐njunction breakdown voltage in this region is lower than that in the radiative region in a LPE layer. This fact suggests that in liquid‐phase epitaxy an impurity concentrated region is formed in the growing process of surface ripples. The existence of the region contributes to the deterioration of the characteristics of devices using thin LPE layers.