International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 09 Issue: 04 | Apr 2022
p-ISSN: 2395-0072
www.irjet.net
COMPARISON OF DUAL SOURCE TFET USING DIFFERENT DIELECTRIC MATERIALS M.PRIYANKA1, K.KALAI SELVI2 1Student,
Dept of ECE,GCE-Tirunelveli, TamilNadu, India Dept of ECE,GCE-Tirunelveli, TamilNadu, India ---------------------------------------------------------------------***--------------------------------------------------------------------1.1 PRINCIPLE Abstract - The potential of high-k gate dielectric materials in 2Professor,
improving the performance of FET. Dielectric material is used to increase the high conductance and reduces leakage. Using the different dielectric materials of HfO2, SiO2 and Si3N4 in dual source TFET are analyzed and compared to get the increasedON current and decreased OFF current. High-k dielectric materials like hafnium dioxide (HfO2) with dielectric constant in the range 22 to 25 give better performance than silicon dioxide and silicon nitride. The performance analysis of TFET with HfO2, SiO2, Si3N4 as gate dielectric is done using SilvacoAtlas TCAD to understand the betterment of behavior of FET with high-k dielectric. FETs with high-k gate dielectric materials can be used in applications where power consumption and thermal stability are crucial[1].
The TFET operation is based on band-to-band tunnelling (BTBT) method. BTBT process creates a tunnelling window through which the tunnelling of carriers from the valence band into the conduction band occurs. When the gate voltage is about to zero, the TFET is in the OFF state. The conduction band in the channel lies on top of the valence band in the source. As a result, BTBT is inhibited and therefore the TFET is in the OFF state with very low drain current. When the gate voltage is increased, the gate voltage modulates the carrier density below the gate and the conduction band in the channel is pushed down. Once sufficiently high voltage is applied to the gate, there's band bending at the source such the valence band in the source and therefore the conduction band within the channel get aligned. As a result, electrons in the valence band in the source will tunnel to the conduction band in the channel. The electrons that tunnel into the channel is swept to the drain terminal by the positive bias of the drain. This forms the premise of operation for an n-type TFET. It ought to be noted that, not like a MOSFET, a TFET is an ambipolar device. For example, an n-type TFET with the key contribution of electrons within the current transport will exhibit a p-type behavior with the major contribution of holes in the current transport, if a negative bias is applied to the gate.
Key Words: Dual source tunnel FET, Band to band tunneling, High-K dielectric material, High conductance
1. INTRODUCTION The exponential increase in number of transistors on an integrated circuit over time was first predicted by Moore’s Law. Since the early 1970s, the metal oxide semiconductorfield-effect-transistor (MOSFET) has been recognized as the most promising device in VLSI circuits, because of its simpler structure, lower cost to fabricate and lower power consumption compared to bipolar and junction field– effect transistor (BJTs and JFETs). The demand for integrated circuits in the industry with greater functionality and lower cost performance requires an increase in chip density which demands scaling of the device. Scaling of silicon dioxide dielectric was once been viewed as an effective approach to enhance transistor performance in complementary-metaloxide-semiconductor (CMOS). In past few decades, reduction of the thickness of gate dielectric below 2 nm, which is close to the physical limit, has led to huge increase in gate leakage current due to obvious tunnelling effect. On further scaling of the device, the leakage currents through Silicon dioxide (SiO2), currently used dielectric, are intolerable due to high power consumption and low breakdown voltage. To continue the downward scaling, high-k dielectric materials are currently inconsideration for gate dielectric in MOSFET devices which play a major role in affecting threshold voltage (Vt). As the name suggest, these materials have high dielectric constant (high k) which improves the oxide capacitance, has low gate leakage current thus providing better stability to the device, lower power dissipation and higher breakdown voltage
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1.2 DIELECTRIC MATERIALS Dielectric materials are substances which are poor conductors of electricity. They are also called as insulators with an effective support of electrostatic fields. The flow of current is kept to a minimum when a dielectric is placed between opposite charged poles without interrupting the electrostatic. Important properties of a dielectric are its ability to support an electrostatic field while dissipating minimal energy in the form of heat, the extent to which a substance concentrates the electrostatic lines of flux. Substances with a low dielectric constant include a perfect vacuum, dry air, and most pure, dry gases such as helium and nitrogen. Materials with moderate dielectric constants include ceramics, distilled water, paper, mica, polyethylene, and glass. Metal oxides, in general, have high dielectric constants. Dielectric materials with high dielectric constants can be used as gate dielectric in TFET. The dielectric material examined in this study in detail is hafnium oxide, silicon
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