A Cut-off Frequency Measurement Platform for Subthreshold TFTs

Despite of low-power consumption and high trans-conductance efficiency, subthreshold TFTs suffer from cut-off frequency rolling down rapidly with gate voltage decrease to the deep subthreshold regime. To characterize cut-off frequency from its definition, it is important to measure the ac components of drain and gate currents. However, the currents of subthreshold TFTs are very low, making it difficult to measure subthreshold currents, in particular ac currents. This paper introduces a platform to measure cut-off frequency for subthreshold TFTs. The results show that the subthreshold TFTs can possess a decent cutoff frequency of above 100 kHz.