Organic field-effect transistors saturation mobility

Fig. 2 (a) Output and (b) transfer characteristics of a near-ideal organic field-effect transistor in hole accumulation, (c) Extraction of mobility and threshold voltage from the square root plot of the saturation current... 

The DC characteristics of the organic transistors were measured in air prior to the application of the rnbber pressnre sensor lihn. The field-effect mobility is 1.4 cmWs in the saturation regime. The on/off ratio is 10 if the off current is defined as the minimum drain current at Vqs = h-40 V, while it is 10 if the off current is measured at Vqs = 0 V. The mobility of the present device is comparable to or slighdy larger than that of amorphous silicon ( 1.0 cmWs). 

Knowledge of the distribution of the electric field in the channel is very useful for a number of reasons. In many organic materials, the mobiUty is electric-field dependent, and an accurate model of the current-voltage characteristics must consider the influence of the electric field on the mobility. The numerically computed potential profile for L— 1.5 m channel length a-6T TFT is shown in Fig. 4. In this device the gate dielectric thickness is 300 nm, and the I-V characteristics exhibit pronounced short-channel effects. As noted in the previous sub-section, short-channel effects are a set of effects which become prominent when the electric field along the channel becomes comparable to the gate field (perpendicular to the channel). The main effects on the transistor characteristics are (1) the saturation characteristics are adversely affected, and, (2) the subthreshold current is increased. 

---