  Ferroelectric field-effect transistors (FE-FETs) consisting of tunable
dielectric layers are utilized to investigate interfacial transport processes.
Large changes in the dielectric constant as a function of temperature are
observed in FE-FETs in conjunction with the ferroelectric to paraelectric
transition. The devices offer a test bed to evaluate specific effects of
polarization on the electrical processes. FE-FETs have dominant contributions
from polarization-fluctuation rather than static dipolar disorder prevalent in
high k paraelectric dielectric-based FETs. Additionally, photo-excitation
measurements in the depletion mode reveal clear features in the FET response at
different temperatures, indicative of different transport regimes.
