High-Frequency Devices

Graphene transistor: Graphene has been an intriguing material with novel physical properties, thanks to its unique atomic structure, such as electron mobility and high elasticity. The bandgap of graphene is very small in spite of being an organic material and is tunable according to the number layers. In the nanoelectronics field, graphene has been employed as a field-effect transistor element. Many types of devices have been developed with high mobility of electron in graphene and tunable bandgap, for instance, top-or bottom-gated devices. The shape of graphene determines the electrical property in the nano scale, so graphene nanoribbon was used to produce elements of devices with different bandgaps. Also, graphene has shown high performance in radio frequency applications. Graphene functional circuits: The conventional functional circuits have mainly made use of Si-based electronics. However, the circuits are stretched to the limits in terms of the maximum frequency, linearity, and power dissipation. Recently, many researchers and industry have carried out research on graphene for supplementing Si electronics because of the former's unique properties. Graphene can provide current density orders of magnitude higher than the most conductive metals, and yet its conductivity can be modulated by an electric field. Additionally, GFET (graphene field-effect transistor) has a tendency to increase its drain current with increasing width of the graphene sheet. Thus, it is believed that graphene-based applications can provide great advances to achieve much higher operating frequencies. Therefore, much research has also focused on graphene with a bandgap, such as the graphene nanoribbon (GNR) and the reduced graphene oxide (rGO). In this chapter, we investigate advanced graphene functional circuits for future real-world applications: amplifier, frequency doubler, multiplier, inverter, logic circuit, mixer, oscillator, sensor, detector, and so on. The self-aligned electrode is a transistor manufacturing feature wherein the refractory-gate electrode region of a metal-oxide-semiconductor FET (MOSFET) is used as a mask for doping the source and drain regions. This technique ensures that the gate will slightly overlap with the edges of the source and the drain. The use of self-aligned electrodes is one of the many innovations that led to the large increase in computing power in the 1970s. Self-aligned electrodes are still used in the most modern integrated circuit processes. Nowadays, carbon materials (carbon nanotube (CNT), graphene, etc.) and quantum materials are studied for the applications of self-aligned electrode. Self-aligned electrode: The self-aligned electrode is used to eliminate the need to align the gate electrode to the source and drain regions of a metal-oxide semiconductor (MOS) transistor during the fabrication process. With self-aligned gates, the parasitic overlap capacitances between the gate and the source as well as between the gate and the drain are substantially reduced, leading to MOS transistors that are faster, smaller, and more reliable than transistors made without them. Particularly important are charge-coupled devices used for image sensors and nonvolatile memory devices using floating silicon-gate structures. These devices have dramatically enlarged the range of functions that could be made with solid-state electronics. In this part, we introduce the history, development, manufacturing, and application of self-aligned electrode. Dielectrophoresis: Dielectrophoresis is one of the most effective methods for fabricating nano devices because it is simple enough to manufacture many devices at once. Thus, much interest is recently focused on dielectrophoresis. However, the principle and finding condition are difficult. Particles are polarized, charged, and magnetized by an external field to move toward the direction where the change is dramatic. Dielectrophoretic forces are determined by certain parameters including the particles, the geometry, and the external field. Recently, many research groups have been trying to utilize dielectrophoresis as a fabrication method. In this chapter, we elaborate on the history, theory, and application of dielectrophoresis.