Comparison between the crystallization processes by laser and furnace annealing of pure and doped a-Si:H

A comparison between the annealing processes is made for undoped hydrogenated amorphous Si (a-Si:H), boron and phosphorus doped amorphous silicon. It is found that in all cases the crystallization onset in the furnace always occurs at higher temperature than for the laser-annealed material. The free-carrier phonon interaction shows up in furnace-annealed doped a-Si but is not seen in laser-annealed doped a-Si which has not been melted. The laser annealing crystallization before melting is never perfect, the size of microcrystals depends on the nature of the doping. The physical model which explains the experimental results is based on the existence of electron-assisted short-lived large energy fluctuations of Si atoms jumping from unstable positions in a-Si:H to more stable ones in crystalline materials.