Figure 3: DOFET measurements and parameters.
When it is not specified, the applied voltages are: VS=0 V, VD=−1 V, VCS=0 V, VCD=0 V, and the transistors geometries are: W=100 μm, L=12.5 μm. (a) Width-normalized contact resistance RP as a function of the gate voltage VG. RP is calculated with the method26. In the conventional OFET (viz. without CS and CD), RP decreases with VG, whereas in the DOFET, RP is independent of VG. When the control source is biased at VCS=+5 V, the DOFET works as a conventional coplanar OFET. (b) RP vs VCS at various VG measured on two nominally identical DOFETs. When VCS<−10 V, RP is the same for both the DOFETs and it is independent of both VG and VCS. Inset: measured output characteristics of a DOFET at several VCS. (c) Maximum overall field-effect mobility vs VCS. The inset shows the field-effect mobility as a function of the gate voltage: μFE=(L/W) (∂ID/∂VG)/(Ci VD). The × symbol is the maximum value of each curve. (d) Threshold voltage (VTH) as a function of VCS. VTH is the intercept to the VG-axis of the ID linear fit. Inset: Subthreshold slope as a function of VCS. (e) Normalized output characteristics of the DOFET measured at various VCD. ID is normalized by its maximum value at VD=−30 V. In saturation, the DOFET is an ideal current generator because the current is diffusion driven. The most important short-channel effect due to the channel-length modulation vanishes. The VCD controls the charge extraction at the drain electrode, which has a strong impact on the output conductance (gO=∂ID/∂VD). (f) Normalized output characteristics of a DOFET and two conventional OFETs (viz. without CS and CD).
