Roles of Electrons and Holes in the Luminescence of Rare-Earth-Doped Semiconductors

The roles of electrons and holes in the photoexcitation of a samarium-doped titanium dioxide (TiO2:Sm) thin film were investigated with electrical measurement techniques. To determine these roles, the holes were selectively injected into TiO2:Sm by using a distinctive sample structure involving a silicon oxide interface layer between TiO2:Sm and a conductive silicon substrate. Since the midgap states of the silicon oxide act as a barrier to the electrons in a positive DC bias V-DC, the selective injection of holes can be realized for V-DC>0. The combination of the photoexcited dielectric relaxation technique, that is, the frequency dispersion measurement of complex impedance under excitation light, with the selective injection technique revealed that Sm was excited by electron trapping with a slower response rate of similar to 12 Hz and the subsequent recombination with holes in TiO2 hosts with a faster response rate of similar to 950 Hz. (c) 2013 Wiley Periodicals, Inc. Electron Comm Jpn, 96(11): 1-7, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com).