posted on 2017-01-13, 00:00authored byMohamad I. Nugraha, Roger Häusermann, Shun Watanabe, Hiroyuki Matsui, Mykhailo Sytnyk, Wolfgang Heiss, Jun Takeya, Maria A. Loi
We
perform a quantitative analysis of the trap density of states (trap
DOS) in PbS quantum dot field-effect transistors (QD-FETs), which
utilize several polymer gate insulators with a wide range of dielectric
constants. With increasing gate dielectric constant, we observe increasing
trap DOS close to the lowest unoccupied molecular orbital (LUMO) of
the QDs. In addition, this increase is also consistently followed
by broadening of the trap DOS. We rationalize that the increase and
broadening of the spectral trap distribution originate from dipolar
disorder as well as polaronic interactions, which are appearing at
strong dielectric polarization. Interestingly, the increased polaron-induced
traps do not show any negative effect on the charge carrier mobility
in our QD devices at the highest applied gate voltage, giving the
possibility to fabricate efficient low-voltage QD devices without
suppressing carrier transport.