We investigate low frequency conductivity noise in the drain-source channel of organic material field-effect transistors by measuring the spectra of current fluctuations for several values of the gate voltage V gs and drain voltage V ds and find that it is 1/f . The samples are biased in the ohmic range of the applied V ds . The relative current 1/f noise is inversely proportional to the charge carrier numbers N generated by illumination or by varying the gate-source voltage. Hooge's empirical relation for the 1/f noise is validated for these organic semiconductors with an ␣Х0.01 for poly-thienylene vinylene and about 100 for pentacene thin film transistors. From geometry dependence of the noise we conclude that series resistance can be ignored for poly-thienylene vinylene field-effect transistors. However, some pentacene samples suffer from a noisy series resistance to the channel resistance. From the 1/f noise dependence on geometry and gate voltage bias we conclude that it can be used as a diagnostic tool for device quality assessment.
We measure the contact resistance and 1/f noise on n-type GaN samples grown by various vapour phase epitaxy (VPE) technologies. Contacts are made in a linear transmission line geometry (TLM). In some samples the metal semiconductor contact noise dominates. This 1/f noise spans over 4 decades. In other samples the bulk noise dominates. This 1/f noise is described by the empirical relation S R /R 2 =α/Nf.
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