JUNCTIONLESS TRANSISTOR

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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.

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.

STRUCTURE OF JUNCTIONLESS TRANSISTOR

Gated trans-resistor.

No junction.

Zero Doping concentration gradient.

Nano scale dimensions and high doping concentrations.

FABRICATION PROCESS

Uniform Doping concentration.Bulk conduction.Beam lithography for nanowire and gates

For n-channeldevices

dopant: arsenic

channel concentration:

gate material: P+ polysilicon

INCREASING GATE VOLTAGE

At a Vd of 50 mV

INCREASING DRAIN VOLTAGE

Measured ID(VD) of N- and P-channeljunctionless transistors. L=1um, W=20nm

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.

Temperature dependence

Short-channel effects:Junctionless vs. Inversion-mode device

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

News feeds

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.

• They have near-ideal sub threshold slope,extremely low leakage currents, and less degradation of mobility with gate voltage and temperature than classical transistors.

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.

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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