The Role of Vacancies and Dopants in Si Solid-Phase Epitaxial Crystallization

The role and interaction of vacancies and dopants in the crystallization of amorphous Si (a-Si) by solid-phase epitaxy (SPE) was investigated. To this end, we studied: (i) the solid-phase epitaxy rate measured by time-resolved reflectivity (TRR), (ii) the dopant and carrier concentrations measured by secondary ion mass spectrometry (SIMS) and spreading resistance (SR) analysis, and (iii) the vacancy concentration measured by positron annihilation spectroscopy (PAS). Phosphorus was implanted into a-Si on Si (001), which was previously amorphized by 29Si+ implantation, to create a nonuniform P doping profile. Phosphorus doped samples compensated with a similar boron profile were also studied. Samples were vacuum annealed for various times so that the amorphous-crystal interface was stopped at various depths providing frozen frames of the SPE process. These samples were then studied with PAS to investigate the vacancy population and to identify the impurity-defect complexes. Using this method, we have observed a population of phosphorus-vacancy complexes in the epitaxial layer.