Low-Frequency Noise in Polymer Transistors

The low-frequency noise (LFN) properties of field-effect transistors (FETs) using polymers as the semiconducting substrate material are investigated and explained in terms of the nonstationary mobility µ in the semiconducting polymer. In the frequency $(f)$ range $f < 1\text{kHz}$ it was found that ${1}/f$ noise prevails over other types of LFN in these polymer FETs (PFETs). The spectral density ${S}_{r}$ of LFN of the drain current $I_{D}$ is proportional to the DC power $V_{DS}\cdot I_{D}$ applied to the PFETs channel, from the ohmic to the saturation modes of device operation. In addition, $S_{I}$ is affected by the carrier mobility µ in PFETs channel, as µ in organic FETs is dependent on the biasing. Thus, SI can have an additional sensitivity to $I_{D}$, that is, $S_{I}\propto(V_{DS}\cdot I_{D})^{1-{k}}$, where $k\sim 0.1$. In general, the $1/fLFN$ of PFETs follows the relations that have been obtained for crystal and inorganic FETs with minor correction for nonstationary mobility µ.