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

Compositionally undulating step-graded Al(Ga)In_xAs (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 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.