Compositionally undulating step-graded Al(Ga)InxAs (x =0.05-0.52) buffers with the following InP layer were grown by metal-organic chemical vapor deposition (MOCVD) on (001) GaAs with a 15° miscut.The dislocation distribution and tilts of the epilayers were examined using x-ray rocking curve and (004) reciprocal space maps (RSM) along two orthogonal directions.The results suggested that such reverse-graded layers have different effects on α and β dislocations.A higher dislocation density was observed along the [110] direction and an epilayer tilt of-1.43° was attained in the [1-10] direction when a reverse-graded layer strategy was employed.However,for conventional step-graded samples,the dislocation density is normally higher along the [1-10] direction.