A B-doped superlattice which consisted of three B spikes, separated by 170nm of undoped Si, was grown by means of molecular beam epitaxy and was used to study changes in point defects following Si implantation. After molecular beam epitaxial growth, the wafer was implanted with 146keV or 292keV Si+ to a dose of 5 x 1015/cm2 at 77K. This implantation produced amorphous layers with depths that coincided with those of the middle B peak, or just below the deepest B peak. The samples were then annealed at 800C in Ar. Secondary-ion mass spectrometry and transmission electron microscopy were used to monitor the diffusion of the B spikes and the evolution of the extended defects during annealing. At lower implantation energies, an enhancement of the B diffusivity by over 500 times was observed for both the surface B spike and for the deepest B spike. At higher implantation energies, the results showed conclusively that the back-flow of interstitials into the re-grown region arose from end-of-range damage, just below the amorphous/crystalline interface. It was concluded that, for these implantation conditions, the end-of-range damage did not act as a barrier to the flow of interstitials to the surface. In addition, it was noted that B in re-grown Si did not cluster; whereas the B below the amorphous/crystalline interface did do so.

K.S.Jones, R.G.Elliman, M.M.Petravic, P.Kringhøj: Applied Physics Letters, 1996, 68[22], 3111-3