CRYSTALLINE PROPERTIES OF LASER CRYSTALLIZED SILICON FILMS

The carrier mobility of phosphorus-doped laser crystallized polycrysta lline silicon (poly-Si) films was investigated. An analysis of the fre e carrier optical absorption spectra gave the carrier mobility 6-11 cm (2)/V.s, for the laser energy between 140 (the crystallization thresho ld) and 280 mJ/cm(2). The mobility increased as the temperature decrea sed from 473 K to 77 K because of the reduced carrier scattering by th e lattice vibration as in single crystalline silicon. On the other han d, the carrier mobility obtained by the Hall effect measurements incre ased from 1 to 5 cm(2)/V.s 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 barri er at the grain boundary.