MODELING OF ELECTRONIC DEVICES CHARACTERISTICS BASED ON ARMCHAIR GRAPHENE NANORIBBON MATERIAL FOR LOW POWER AND HIGH SPEED DEVICE APPLICATION

• Main Author: SUHENDI (NIM : 30210007), ENDI
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/26936
• Institution: Institut Teknologi Bandung

Miniaturization of silicon complementary metal–oxide–semiconductor (CMOS) devices has given remarkable improvements to computer performance such as switching speed, density, and functionality. However, the continuous reduction of silicon CMOS device dimension has resulted in high power consumption due to high leakage currents that degrade the switching ratio of ‘on’ and ‘off’ currents (ION/IOFF) at low supply voltages. One of devices that proposed to replace silicon CMOS is a tunnel field effect transistor (TFET). A TFET use band-to-band electron tunneling to reduce IOFF so that enhancing ION/IOFF and to make steeper subthreshold swing. <br /> <br /> The search for new materials with properties that can be better controlled by the electric field in TFETs has been continuing. One of alternative material that is currently widely studied is Graphene. Graphene is a two-dimensional material that has interesting properties such as: high carrier mobility, very light effective mass (toward zero), one atom thickness, planar geometry and the manufacturing process are compatible with conventional silicon technology. Graphene has the potential to be a replacement of silicon material for future applications of electronic devices. Armchair graphene nanoribbon (AGNR) which has a band gap energy depending on its width, opened the application of this material for logic devices such as tunnel field-effect transistors/TFET. <br /> <br /> vi <br /> <br /> Research on the modeling of graphene nanoribbon application for electronics devices have been carried out. Devices being simulated are a p-n junction diode and TFET. The characteristics modeling of electronic devices graphene nanoribbon p-n junction diode is the relations between the tunneling current with the bias voltage. The calculation of the transmittance and the tunneling current in this device is using the Dirac ‘like’ equation with the transfer matrix method/TMM. As a comparison, the transmittance and the tunneling current are also calculated using the Schrödinger equation with the TMM and WKB approach. The formulation and the calculation of the tunneling current in p-n junction and TFET devices based AGNR material using the Dirac like equation and the TMM are a novelty and it has not been done by other researchers. <br /> <br /> The characteristics of electronic device AGNR p-n junction diode are influenced by the geometry and the temperature. The tunneling current increases with the width of AGNR and the electric field in the depletion region. The tunneling current increases as the temperature increases. The maximum current density in the AGNR p-n junction diode increases when the electric field in the depletion region increases. The necessary width of AGNR to make the maximum current density gets smaller with increasing electric field. The tunneling currents in the AGNR p-n junction diode calculated using the Schrödinger equation through MMT is larger than that using Dirac ‘like’ equation. However, the increase in tunneling current has a similar pattern. Unlike the calculations through MMT, WKB approach has its own pattern and the difference is quite striking. <br /> <br /> Modeling of the potential profile in the graphene nanoribbon tunnel field-effect transistor/AGNR-TFET has been done using a self-consistency method between the Dirac ‘like’ equation and a Poisson equation with Finite Difference Time Domain/FDTD approach. These formulation and calculation are a novelty and it has not been done by other researchers. As a comparison, the potential profile is also calculated using the self-consistency method between the Schrödinger equation and the Poisson equation. The calculations result shows that there are <br /> <br /> vii <br /> <br /> differences on the potential energy in the AGNR-TFET devices, although the differences are very small. <br /> <br /> The characteristics of electronic devices AGNR-TFET has been also modeled in the form of relation between tunneling currents with the source voltages and the drain voltages. The transmittance and the tunneling current are obtained by using the Dirac ‘like’ equation with the transfer matrix method. As a comparison, it is also calculated using the Schrödinger equation with the transfer matrix method and WKB approach. <br /> <br /> The characteristics of electronic device AGNR-TFET are influenced by the geometry and the temperature. The tunneling current increases with the width of AGNR. The larger channel length, the smaller tunneling currents occurs. The tunneling currents increase when the oxide thickness and the temperature decrease. The subthreshold swing of AGNR-TFET also depends on the geometry factors. It decreases by enlarging the length of AGNR and reducing the width of AGNR and the oxide thickness. The tunneling current on AGNR-TFET device calculated by using the Dirac ‘like’ equation is smaller than that calculated using the Schrödinger equation. The drain current versus gate voltage characteristic calculated by using Dirac like equation for lower Fermi velocity has similar characteristic with that calculated using the Schrödinger equation. <br /> <br /> The modeled of AGNR-TFET devices has the following characteristics: the threshold voltage is around 0,01-0,02 V, power OFF is 0,0000025 &#956;W/&#956;m, power ON is 2,2 &#956;W/&#956;m and the subthreshold swing is 5 mV/dec. From these characteristics, the AGNR-TFET devices is suitable for the application of low-power and high-speed devices.