Continuum Analysis of Cooperative Pit/Island Formation and Stability in SiGe on Si(100)

Abstract

AbstractRecent experimental work (J. Gray, R.Hull and J. Floro, App. Phys. Lett. Vol 81, No 13, 2002) has investigated the cooperative nucleation and growth of pits and islanding at pit edges in SiGe/Si(100) epitaxial films. The pits, which are observed to form under certain growth conditions, evolve along with the islands until a complete island wall is formed around the pit's periphery. Once formed the pit'island configuration exhibits a surprising stability, with no further lateral growth during continued deposition or annealing. The pits consists of low energy {501} facets (inverted {501} pyramid) and the islands surrounding the pit also exhibiting faceting. Elastic finite element analyses of these configurations were carried out to investigate the dependence of strain energy and surface stress on pit/island geometry. In particular, our results provide insight as to the mechanism responsible for the observed size stability of the pit/island structure once it has become fully developed. Surface stress gradients arising from the geometry are also found to be responsible for the observed initial island formation at the center of pit edges during growth.