Dislocation distributions and tilts in Al(Ga)InAs reverse-graded layers grown on misorientated GaAs substrates

Compositionally undulating step-graded Al(Ga)In x As (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 110 directions. The results suggested that such reverse-graded layers have different effects on ? and ? 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.