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. [ABSTRACT FROM AUTHOR]