Advantages of thin interfaces in step-graded buffer structures

The effect of graded interfaces in step-graded buffer structures on crystal relaxation efficiency is investigated by transmission electron microscopy and double crystal X-ray diffraction. A higher recombination rate leading to higher edge dislocation densities and a strong diminution of the tilt, is evidenced when graded interfaces are used. The latter feature is a consequence of the poor stability of dislocation multiplication sources in graded interfaces. The lower strain energy release of dislocation segments and a diminution of the pinning points in graded interfaces reduce the lifetime of dislocations sources, producing a better distribution of Burgers vector in the misfit dislocations array.