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INTRODUCTION
All existing transistors junctions with junction are P–N junction Heterojunction,Scotty junction,MOSFET, MESFET.
The junctionless transistor (JLT) is a multigate FET with no PN nor N+N or P+P junctions.
The device is basically a resistor in which the mobile carrier density can be modulated by the gate.
Uniformly doped nanowire without junctions with a wrap-around gate.
No junctions and no doping concentration gradients. They have near-ideal sub threshold slope,extremely low leakage
currents, and less degradation of mobility with gate voltage and temperature than classical transistors.
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INTRODUCTION
• …• ,,• Transistors are becoming so tiny that it is becoming
increasingly difficult to create high-quality junctions.• In particular, it is very difficult to change the doping
concentration of a material over distances shorter than about 10 nm.
• Junctionless transistors could therefore help chipmakers continue to make smaller and smaller devices.
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STRUCTURE OF JUNCTIONLESS TRANSISTOR
Gated trans-resistor.
No junction.
Zero Doping concentration gradient.
Nano scale dimensions and high doping concentrations.
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FABRICATION PROCESS
Uniform Doping concentration.Bulk conduction.Beam lithography for nanowire and gates
For n-channeldevices
dopant: arsenic
channel concentration:
gate material: P+ polysilicon
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INCREASING GATE VOLTAGE
At a Vd of 50 mV
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INCREASING DRAIN VOLTAGE
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Measured ID(VD) of N- and P-channeljunctionless transistors. L=1um, W=20nm
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Measured ID(VG) of N- and P-channeljunctionless transistors. L=1um, W=20nm
ID, versus gate voltage, VG, for a drain voltage of +1 V in n-type and p-type devices having a width of 30 nm and a length of 1 mm.
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Temperature dependence
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Short-channel effects:Junctionless vs. Inversion-mode device
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TYPES OF JUNCTIONLESS TRANSISTOR
Junctionless MuGFET:• This device has no junctions, a simpler fabrication process,
less variability and better electrical property than classical inversion mode.
Bulk Planar Junctionless Transistor (BPJLT):• Highly scalable source–drain junction- free field-effect
transistor. It is thus junctionless in the source–channel–drain path but needs a junction in the vertical direction for isolation purposes
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News feeds
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Adv & Dis
• the lateral extension of the S/D depletion charges in the channel region are causing short-channel effects such as DIBL and degraded subthreshold slope. These are absent in a JLT
• Further improvement of the short-channel effects can be obtained by increasing the extension of the gate control deeper in the source and drain regions using high-κ spacers.
• one disadvantage of conventional junctionless transistors is that they suffer from poor short-channel control.
• junctionless devices have the potential to operate at faster and use less energy than the conventional transistors used in today's microprocessors.
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• They have near-ideal sub threshold slope,extremely low leakage currents, and less degradation of mobility with gate voltage and temperature than classical transistors.
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CONCLUSION
The devices have no junctions and are made in n+ or p+ silicon nanowires.
The devices have full CMOS functionality no junctions or doping gradients less sensitive to thermal budget issues than regular CMOS
devices. a near-ideal subthreshold slope, close to60 mV/dec at room
temperature extremely low leakage currents. Gated resistors exhibit less degradation of mobility than
classical transistors when the gate voltage is increased.
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Reference
Jean-Pierre ColingeTyndall National Institute, University College CorkLee Maltings, Cork, Ireland” Junctionless Transistors” 978-1-4673-0836-6/12/$31.00 ©2012 IEEE
Twinkal Solankia, Nilesh Parmar” A Review paper: A Comprehensive study of Junctionless transistor”National Conference on Recent Trends in Engineering & Technology
A. Kamath, Z. X. Chen, N. Shen, X. Li, N. Singh, G. Q. Lo, and D.-L. Kwong“Junctionless CMOS Transistors with Independent Double Gates” International Journal of Information and Electronics Engineering, Vol. 3, No. 1, January 2013.
Baruch Feldman”Simulations of electronictransport in ultra-thin andultra-shortjunctionlesstransistors”
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