Author details

is another way of increasing Cg. The reduction in C<sup>p</sup> may also be obtained by decreasing a width of the gate contact and increasing the distance between the contacts and gate contacts. However, the increase in the distance between electrodes is limited by increase of the serial resistance Rc. Actually, Eq. (13) describes the cut-off frequency of the active region of the transistor, i.e., the channel region under the gate, the output AC signal is measured when the current flows through the load resistance R. Resistance R<sup>c</sup> is shunted by a capacitance of Cp, therefore, the cut-off frequency of AC signals cannot exceed ω<sup>1</sup> ¼ 1/(RcCp). Since R<sup>c</sup> increases with increasing interelectrode distance, the effect of increasing this distance is significantly

Thus, reducing the size of the active area of the transistors leads to an increase in the cut-off frequency, which is the main physical reason for the miniaturization. However, as mentioned in Section 1, miniaturization of transistors has led to the increase in the leakage current, which significantly increases energy consumption and reduces the prospects for further development in this direction to zero. The use of resonant tunneling can significantly reduce leakage currents, but it is necessary to use a carrier system with reduced dimensions. These systems which appear in semiconductor nanoheterostructures, recently also actively studied the carbon nanomaterials. Here, there is a new problem with miniaturization. When reduction of Lch size occurs up to 20 nm, lateral size-quantization takes place in the two-dimensional gate and channel. This significantly degrades the resonant nature of tunneling, and nullifies efforts to suppress it, as demonstrated in the study of RTD of nanometer sizes [8]. However, to date, it has been shown that a RTD with a transverse size of 5 μm, is capable of operating at frequencies above 4 THz, which is 2 orders of magnitude higher frequencies of modern high-frequency transistors. A major obstacle to the wide use of RTD is the high cost of producing semiconductor nanoheterostructures, which requires the involvement of molecular beam epitaxy. However, the development of relatively cheap methods of obtaining carbon nanomaterials creates serious prospects of using such materials for the creation of RTD. RTD have already been successfully created on the base of graphene

In summarizing, we can state that application of resonant tunneling can significantly increase the operating speed of the FET and reduce leakage currents. However, the application of 2DCS systems imposes new restrictions on the miniaturization, reducing her prospects to almost zero. However, even relatively large RTD already working on the frequencies exceeding the frequencies of the transistors. It is shown that devices based on resonant tunneling are able to replace the conventional FET. The main problem of widespread use of such devices today is a significant high cost of the technology of molecular-beam epitaxy. Possible further development of technology toward a carbon nanomaterials. Carbon nanomaterials might allow highquality RTD, which is significantly cheaper than semiconductor materials. In this case, we

5.2. Size-quantization and its effect on resonant tunneling

40 Different Types of Field-Effect Transistors - Theory and Applications

films [19, 20], but their quality is inferior to semiconductor films.

reduced.

6. Conclusion

Vladimir Popov

Address all correspondence to: sokhatiy@gmail.com

Institute of Microelectronics Technology of Russian Academy of Science, Chernogolovka, Russia
