Crystalline properties of laser crystallized silicon films

The carrier mobility of phosphorus-doped laser crystallized polycrystalline silicon (poly-Si) films was investigated. An analysis of the free carrier optical absorption spectra gave the carrier mobility, 6-11 cm2/V&middots, for the laser energy between 140 (the crystallization threshold) and 280 mJ/cm2. The mobility increased as the temperature decreased from 473 K to 77 K because of the reduced carrier scattering by the lattice vibration as in single crystalline silicon. On the other hand, the carrier mobility obtained by the Hall effect measurements increased from 1 to 5 cm2/V&middots as the laser energy increased. The mobility for samples crystallized near the crystalline threshold decreased as the temperature decreased from 473 K to 77 K. This is probably caused by lack of the thermal excitation energy for crossing the energy barrier at the grain boundary.