Field-effect transistor current-voltage curves

A similar situation exists in an insulated gate structure the difference between the WF of the semiconductor and the gate metal adjacent to the insulator causes a deficiency or an excess of electrons in the semiconductor at its interface with the insulator. In the semiconductor/insulator/metal diodes the amount of the excess charge at the semiconductor plate is determined from the capacitance-voltage curves while in a field-effect transistor the excess charge at the semiconductor/insulator interface is related to the magnitude of the drain-to-source current [13]. In either case the observed WF difference contains the contribution from both the bulk and from the surface (or interface). 

Figure 13.16 shows a SiNW 4 p.m in length and 9.5 nm in width. Figure 13.16a shows the silicon oxide mask. The thickness of the fabricated mask is about 3 nm. After etching, the SiNW is contacted to two platinum electrodes (Fig. 13.16b). The fabricated SiNW is the main element of a field-effect transistor formed by introducing a gate electrode. Here, the gate electrode is situated at the back of a silicon-on-insulator wafer. The output and transfer characteristics of the transistor formed with the SiNW described above are shown in Fig. 13.16d. The output curve (left panel) shows a clear dependence on the gate voltage. The off-state drain current leakage is about 10 A. The device shown above has an on/off current ratio of 10, and it can be used to develop very sensitive biomolecular sensors.

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