Bias-stress effect in 1,2-ethanedithiol-treated PbS quantum dot field-effect transistors

Publication Type:

Journal Article

Source:

ACS Nano, ACS Publications, Volume 6, Issue 4, p.3121-3127 (2012)

ISBN:

1936-0851

Keywords:

2012, 2013 and earlier

Abstract:

We investigate the bias-stress effect in field-effect transistors (FETs) consisting of 1,2-ethanedithiol-treated PbS quantum dot (QD) films as
charge transport layers in a top-gated configuration. The FETs exhibit
ambipolar operation with typical mobilities on the order of μ(e) = 8 ×
10(-3) cm(2) V(-1) s(-1) in n-channel operation and μ(h) = 1 × 10(-3)
cm(2) V(-1) s(-1) in p-channel operation. When the FET is turned on in
n-channel or p-channel mode, the established drain-source current rapidly
decreases from its initial magnitude in a stretched exponential decay,
manifesting the bias-stress effect. The choice of dielectric is found to
have little effect on the characteristics of this bias-stress effect,
leading us to conclude that the associated charge-trapping process
originates within the QD film itself. Measurements of bias-stress-induced
time-dependent decays in the drain-source current (I(DS)) are well fit to
stretched exponential functions, and the time constants of these decays in
n-channel and p-channel operation are found to follow thermally activated
(Arrhenius) behavior. Measurements as a function of QD size reveal that
the stressing process in n-channel operation is faster for QDs of a
smaller diameter while stress in p-channel operation is found to be
relatively invariant to QD size. Our results are consistent with a
mechanism in which field-induced nanoscale morphological changes within
the QD film result in screening of the applied gate field. This phenomenon
is entirely recoverable, which allows us to repeatedly observe bias stress
and recovery characteristics on the same device. This work elucidates
aspects of charge transport in chemically treated lead chalcogenide QD
films and is of relevance to ongoing investigations toward employing these
films in optoelectronic devices.