FREE-CARRIER ABSORPTION IN MICROCRYSTALLINE SILICON THIN-FILMS PREPARED BY VERY-HIGH-FREQUENCY GLOW-DISCHARGE

The optical properties of heavily phosphorus- and boron-doped microcry stalline silicon thin films prepared at 70 MHz in a silane glow discha rge have been measured in the visible and near infrared. The experimen tal data have been analysed in terms of the classical Drude model for free-carrier absorption. Excellent agreement between the carrier conce ntration deduced from the dispersion of the refractive index and that obtained by Hall-effect measurements has been obtained. A self-consist ent analysis of (an)(-1) against lambda(-2) led to the determination o f a Drude mobility of 9-15 cm(2) V-1 s(-1) in n-type material. The pos sible reasons for the deviation from room-temperature Hall values mu(H ) of about 1-3 cm(2) V-1 s(-1) are discussed.