Graphene Tunneling Transit-Time Terahertz Oscillator Based on Electrically Induced p–i–n Junction

Abstract

We propose and analize a graphene tunneling transit time device based on a heterostructure with a lateral p-i-n junction electrically induced in the graphene layer by the applied gate voltages of different polarity. The depleted i-section of the graphene layer (between the gates) serves as both the tunneling injector and the transit region. Using the developed device model, we demonstrate that the ballistic transit of electrons and holes generated due to interband tunneling in the i-section results in the negative ac conductance in the terahertz frequency range, so that the device can serve as a terahertz oscillator.Graphene is considered as a promising candidate for different future electronic and optoelectronic devices. Its most distinctive features beneficial for device applications include high electron and hole mobilities in a wide range of temperatures, the possibility of bandgap engineering (creation of the graphene-based structures with the energy gap from zero to fairly large values), formation of electrically induced lateral p-n junctions (see, for instance, [1,2,3,4,5]).The operation of graphene field-effect transistors (GFETs) is accompanied by the formation of the lateral np-n (or p-n-p) junction under the controlling (top) gate and the pertinent energy barrier [6,7,8,9]. The tunneling across such a n-p-n junction prevents the achievement of a low off-state current [9]. This limits possible realization of G-FETs in large scale digital electronic circuits and forces to consider the graphene structures in which the energy gap is reinstated (graphene nanoribbons and graphene bilayers with the energy gap open by the transverse electric field) [10,11,12,13,14,15,16].Unique properties of graphene already produced not only using peeling technology but also epitaxial methods as well as graphene nanoribbons and bilayers, particularly, experimental evidences of the possibility of ballistic electron and hole transport in samples with several micrometer sizes even at room temperatures (see, for instance, Refs. [17,18]) stimulate inventions of different graphene-based devices which could not be realized the past using the customary materials.In this paper, we propose a transit-time oscillator which can operate in the terahertz (THz) range of frequencies and substantiate the operational principle of the * Electronic mail: v-ryzhii@u-aizu.ac.jp device. The operation of the device in question is associated with the tunneling electron injection in an electrically induced reverse biased lateral p-i-n junction and the electron and hole transit-time effects in its depleted section. In the following, this device is referred to as the graphene tunneling transit-time (G-TUNNETT) terahertz oscillator. The tunneling generation through the zero energy gap and propagation of electrons and holes with their directed velocity v x close to the characteristic velocity v W ≃ 10 8 cm/s of the graphene energy spectrum (v x ∼ v W ), can provides significant advantages of G-TUNNETTs in comparison with the existing and discussed TUNNETT...

Terahertz science and technology of carbon nanomaterials

“…The predicted net plasmon gain for different electronhole densities at 300 K is shown in figure 9. Several plasmonic amplifiers and oscillations in graphene devices have been proposed for generating THz waves [228][229][230][231][232]. It has been predicted that THz lasing can be realized at room temperature in optically pumped lasers utilizing Fabry-Pérot resonators [224,233] and dielectric waveguides [234].…”

Electrically inducedn−i−pjunctions in multiple graphene layer structures

“…This current can be calculated using the following formula which follows from the expression for the tunneling probability in GLs [1,2] (see, for instance [5]):…”

“…The possibility to form electrically-induced n-p and n-i-p junctions [1][2][3] in gated graphene layers (GLs), as well as lateral arrays of graphene nanoribbons and graphene bilayer opens up prospects of creation novel electronic and optoelectronic devices [4][5][6][7][8]. In contrast to GL structures with chemically doped n-and p-region in the GL structures with electrically-induced n-p and n-i-p junctions, there is a possibility of their voltage control.…”

Graphene‐Based Terahertz Devices: Concepts and Characteristics

“…6(a) but at reverse bias can also be used in GL tunneling transit-time (G-TUNNETT) devices. 17 The G-TUNNETT structure under consideration and its band diagram (at an applied source-drain voltage V such that the lateral pin junction is reverse biased) are schematically shown in Figs. 6(a) and (b), respectively.…”