Electrical Instabilities and 1/f Noise in Organic Pentacene Thin Film Transistors

ABSTRACTWe report on the influence of Bias-Temperature Stress (BTS) on the pentacene Thin Film Transistors (TFTs) electrical characteristics and on their 1/f noise level. The gate BTS primarily affects the TFT threshold voltage, leaving both mobility and sub-threshold slope values almost unchanged. The degree of the threshold voltage shift induced by the positive or negative BTS depends on the TFT design and the BTS parameters. The current-voltage characteristics time dependence of the organic TFTs, subjected to the BTS, resembles that for amorphous-Si TFTs. The results of the 1/f noise measurements in the organic TFTs allowed us to conclude that the gate BTS primarily affects the TFT contact regions, resulting in the increase of both the contact noise and the contact resistance.</jats:p

1/f Noise Behavior in Pentacene Organic Thin Film Transistors

ABSTRACTWe studied the low frequency noise in top-contact pentacene Thin Film Transistors (TFTs). The relative spectral noise density of the drain current fluctuations SI/I2 had a form of 1/f noise in the measured frequency range 1Hz - 3.5kHz.Our studies of the noise dependencies on the gate-source VGS and drain-source VDS voltages showed that the dependencies differed from those observed for conducting polymers and resembled those reported for crystalline Si n-MOSFETs.To compare the device noise level with those of other devices and materials, we extracted the Hooge parameter α. In order to calculate the total number of carriers we used a model simulating the device DC characteristics, similar to that for amorphous Si TFTs. The extracted Hooge parameter was 0.04. For an organic material this is an extremely small value, which is three orders of magnitude smaller that the Hooge parameter values reported for conducting polymers and only several times higher than the values for amorphous Si TFTs.</jats:p