Semiconductor-Metal Transition in Te by Laser Irradiation

概要

論文の詳細を見る
A transition to a state of metallic photoconductivity as high as 3×10^5Ω^<-1> cm^<-1> has been observed at 4.2°K, and 1×10^5Ω^<-1> cm^<-1> at 77°K, in p-type Te which is irradiated by a Q-switched Nd-laser pulse with the peak intensities up to 10^5 W/cm^2 corresponding to excess electron-hole pairs of 7×10^<17>/cm^3. The electron-hole pair density is estimated from the measured photoconductance in terms of the band-to-band recombination mechanism of the excited pair. Because of the large indices of refraction and hence the large Bohr radius (〜400 A), the Mott transition to a metallic state takes place with the critical electron-hole pair density of 〜10^<15>/cm^3 which is comparable to the density of majority carriers. The electron-hole pairs, therefore, are unbound for the present range of laser beam intensity and contribute entirely to the electrical conduction. Unlike the case of Ge, a new anomaly in photoconductivity has been observed with respect to the increase in excited electron-hole pair density. The phenomenon, presumably, comes from change in the statistics of the unbound carriers. The estimated density is compared with that deduced from the photomagnetoelctric effect.
東北大学の論文