Graphene-based Field Effect Diode
Introduction
Graphene is a two-dimensional material formed by the combination of carbon atoms [1,2]. Andre Geim et al. produced this material for the first time in 2004 at the University of Manchester [3]. Graphene is a semiconductor with a band gap of zero, in which the electrons act like massless Dirac fermions and show very high mobility (100.000 cm2/V·S) [4]. This material as a single atomic layer is a good conductor of electrical current [4,5]. In addition, the Fermi energy level, and hence the electron and hole concentration, can be changed in Graphene by applying the electric field [[4], [5], [6]]. Accordingly, this material can play a functional role in the electronic and optoelectronic devices [[7], [8], [9]].
One of the most important components in the electronics industry is transistor. Minimization of the transistor size has been continued to advance the silicon-based electronics devices. However, various scientific and technical issues have limited this advancement. Graphene-based technology is an alternative to overcome such limitations in silicon technology [[9], [10], [11]]. Graphene-based transistors have been proposed to take advantage of the peculiar electrical properties of Graphene in the electronics industry [[9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29]]. Field effect transistors (FETs) manufactured using Graphene as an active element can play a significant role in the evolution of the next generation of electronic components [[9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29]]. Graphene can also be used as an electrode (source and drain) as well as the channel layer in any type of FET structure [5], [9,10]. Graphene on a SiO2 substrate has shown a high rate of mobility (10000 cm2/V.s) [30,31]. Therefore, faster and smaller transistors with lower energy consumption and higher thermal dissipation than the silicon transistors can be achieved using Graphene [[9], [10], [11]], [[13], [14], [15], [16]].
One of the major problems with Graphene transistors is the low On/Off current ratio [17]. Different methods have been reported to improve this feature [14,15], [[17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29]]. The absence of a band gap causes effectively that there is no strong saturation behaviour in Graphene transistors. It also causes a low On/Off current ratio, for which the values reported are 2.4 [14], 3 [15], as well as about 5 for single layer top-gated Graphene-FET [19], at room temperature. One reported method to get a higher On/Off current ratio is patterning the Graphene channel, according to which the On/Off ratio obtained has been reported equal to 7 [20]. Creating a band gap in Graphene by changing its physical structure leads to transistors with higher On/Off ratio. Some of these structural modifications are the use of Graphene nanoribbons, Graphene shaping, and the use of multi-layer Graphene. For example, Graphene-based transistors obtained by the use of the Graphene nanoribbons lead to the On/Off ratio of 106 [21], as well as the ratio of 107 [22] and 2✕103 at room temperature [25]. Creating nano holes in Graphene layer can also increase the On/Off current ratio to 2✕103 in [29]. On the other hand, applying a perpendicular electric field can create a band gap up to a few hundred milli-electron volts in bilayer Graphene. This effect results to an On/Off current ratio as high as 100 at room temperature and 103 at cryogenic temperature for double-gate bilayer Graphene field effect transistor [18,19]- [27]. Although the proposed methods have advantages, but they continue to suffer from such limitations as complexity in the fabrication process. Despite many efforts conducted and different methods presented in this area, there is still a need for an efficient and simple structure of Graphene-based transistor.
In this paper, a new structure of a Graphene-based transistor has been designed and simulated. This structure is able to supply less Off-current than the Graphene transistors presented so far and consequently provides high On/Off current ratio. The proposed structure is a Graphene-based Field Effect Diode (G-FED) consisting of a Graphene channel, in which the carrier concentration can be modulated by the two gates over the Graphene channel. To compare the On/Off current ratio, a G-FET with the comparable size is also designed and presented. The current-voltage graphs have been drawn and the carrier concentration has been measured in both On and Off modes. The G-FED shows an on/off current ratio of about 100. This value is about one order of magnitude larger than the On/Off current ratio of a comparable G-FET. Considering the simple structure of G-FED along with the higher On/Off current ratio, this device can be a good functional component in Graphene-based circuits.
Section snippets
Field effect diode (FED)
Fig. 1 shows the structure of a Silicon-based FED. The FED is a field effect component that has been formed to control the current by two gate terminals [[32], [33], [34], [35], [36], [37], [38], [39], [40], [41]]. The FED construction is similar to the MOSFET construction, except that it has two upper gates. Another difference is related to the type of source and drain impurities. In FED, the source and the drain impurities are unlike each other. In addition, by applying voltages with opposite
Graphene-based Filed Effect Diode (G-FED)
The ability to control the electronic properties of materials by applying an external voltage has expanded in modern electronics. In many cases, it is the electric field effect that allows a change in the carrier concentration and, consequently, a change in electrical current of a semiconductor component [42,43]. In the case of Graphene, the electric field of an isolated gate can change the Fermi energy level [44]. This feature leads to design of field effect devices based on Graphene, such as
Results and discussion
DC current-voltage characteristics of G-FED are obtained and the relevant linear and semi-logarithmic results are provided in Fig. 5. Fig. 5 a shows the drain current with respect to the drain voltage VDS. The drain current on a log plot with respect to VDS is demonstrated as the inset of this figure. The linear portion of the plot is indicative of the exponential behaviour of the p-n junction and for an ideal diode has to exhibit a 60mV/decade slope, which is roughly what this plot reveals
Conclusion
83. This paper presents a report on the structure of the Graphene-based field effect diode. Then, the features of the on/off current ratio of this component have been investigated. Given that the on/off current ratio is not optimal in the Graphene transistors, we have presented in this paper a component that has an appropriate on/off current ratio, which is based on the structure of the field effect diode (FED). Here, both the Graphene field effect diode and the Graphene transistor structures
Acknowledgment
This work was supported by Shahid Rajaee Teacher Training university under contract number of 28240.
References (51)
Graphene: carbon in two dimensions
Mater. Today
(2007)- et al.
Graphene based field effect transistors: efforts made towards flexible electronics
Solid State Electron.
(Nov. 2013) - et al.
Mobility extraction and quantum capacitance impact in high performance Graphene field-effect transistor devices
In Electron Devices Meeting. IEEE International
(Dec.2008) - et al.
Mobility in Graphene double gate field effect transistors
Solid State Electron.
(Apr .2008) Atomic Structures of Graphene, Benzene and Methane with Bond Lengths as Sums of the Single, Double and Resonance Bond Radii of Carbon
(2008)- et al.
Electric field effect in atomically thin carbon films
Science
(2004) - et al.
The electronic properties of Graphene
Rev. Mod. Phys.
(Jan. 2009) - et al.
Electric field effect tuning of electron-phonon coupling in Graphene
Phys. Rev. Lett.
(Apr. 2007) - et al.
Photodetectors based on Graphene, other two-dimensional materials and hybrid systems
Nat. Nanotechnol.
(Oct. 2014) - et al.
Graphene-Si Schottky IR detector
IEEE J. Quant. Electron.
(Jul. 2013)