Capacitance/Conductance–Voltage–Frequency Characteristics of ${\rm Au}/{\rm PVC}+{\rm TCNQ}/{\rm p}\hbox{-}{\rm Si}$ Structures in Wide Frequency Range

The energy dependence of the interface states
$(N_{{\rm ss}})$
and relaxation time
$(\tau)$
and capture cross section
$(\sigma_{{\rm p}})$
of
$N_{{\rm ss}}$
in
$({\rm Au}/{\rm PVC}+{\rm TCNQ}/{\rm p}\hbox{-}{\rm Si})$
heterojunction were investigated using high–low frequency capacitance
$(C_{{\rm HF}}-C_{{\rm LF}})$
and conductance method, which contains many capacitance/conductance
$[C/(G/\omega)-V]$
plots. The
$C$
value of the heterojunction increases with decreasing frequency as almost exponentially due to the existence of
$N_{{\rm ss}}$
between metal and semiconductor. The
$N_{{\rm ss}}$
and
$\tau$
values have been obtained in the (0.053-
$E_{{\rm v}}$
)-(0.785-
$E_{{\rm v}}$
)-eV energy range by considering the voltage-dependent surface potential obtained from the lowest measurable frequency
$C{-}V$
curve at 1 kHz. The magnitude of
$N_{{\rm ss}}$
ranges from
$3.88\times 10^{12}~{\rm eV}^{-1}{\rm cm}^{-2}$
to
$3.24\times 10^{{12}}~{\rm eV}^{-1}{\rm cm}^{-2}$
. In the same energy range, the value of
$\tau$
ranges from
$5.73\times 10^{-5}$
to
$1.58\times 10^{-4}~{\rm s}$
and shows almost an exponential increase with increasing bias from the top of the valance band edge toward the midgap of semiconductor. The obtained
$N_{{\rm ss}}$
values from
$C_{{\rm HF}}{-}C_{{\rm LF}}$
and conductance methods are in good agreement with each other for the heterojunction. As a result, the mean value of
$N_{{\rm ss}}$
was found on the order of
$10^{12}~{\rm eV}^{-1}{\rm cm}^{-2}$
and this value is very suitable for an electronic device.