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Nanoscale Science and EngineeringNSF, Arlington, VA

Dec. 6, 2010Eli Yablonovitch, Berkeley EECS Dept.

Electronics / network electricity use

Buildings Electricity: ~2,700 TWh

CommercialResidential

Electronics

Networked~150 TWh ?

Net. Eqt.~ 20 TWh

• U.S. only• Annual figurescirca 2006

• All approximate

One central baseload power plant (about 7 TWh/year)

~290 TWh

Bruce Nordman, LBL

Tel.

• Because power consumption Vdd2

and Vdd (operation voltage) scaling has slowed after 0.13μm node.

High Performance ITRS Roadmap

0.7 V0.8 V0.9 V1.0 V1.1 V1.2 V1.3 V1.8 V2.5 VVdd

16 nm

22 nm

32 nm

45 nm

65 nm

90 nm

0.13 µm

0.18 µm

0.25 µm

Technology Node

Power Usage Rising Faster Than Past Trend

∝

Units:

~40kT/bit of information

0.16 atto-Joules/bit of information

0.16 nano-Watts/Gbit/second

This is about 106 times less energy than we are using today!

What will be the energy cost, per bit processed?

1. Logic energy cost ~40kT per bit processed

2. Storage energy cost ~40kT per bit processed

3. Communications currently >100,000kT per bit processed

.

There are many type of memory possible:1. Flash2. SRAM3. Dram4. Magnetic Spin5. Nano-Electro-Chemical Cells6. Nano-Electro-Mechanical NEMS7. Memristor8. Chalcogenide glass (phase change)9. Carbon Nanotubes

••

Similarly there are many ways to do logic.

But there are not many ways to communicate:

1. Microwaves (electrical)2. Optical

Moore

You?

!

Transistor

fkTR

V

fRkTV

noise

noise

∆=

∆=

4

42

2

What is the energy cost for electrical communication?

Signal Noise PowerEnergy per bit≥ = 4kT per bit

All information processing costs ~ 40kT per bit. (for good Signal-to-Noise Ratio)

Great!

So what’s the problem?

{

mVolt1V

CqqkT4VCq

qkT4V

C1kT4V

RC1RkT4V

fRkT4V

Volts10mVolts100noise

2noise

2noise

2noise

2noise

≈

×=

×=

×=

=

∆=

µ

//321

The natural voltage range for wired communication is rather low:

The thermally activated device wants at least one electron at ~1Volt.

The wire wants1000 electrons at 1mVolt each.

(to fulfill the signal-to-noise requirement >1eV of energy)

Voltage Matching Crisis at the nano-scale!

If you ignore it the penalty will be (1Volt/1mVolt)2 = 106

The natural voltage range for a thermally activated switch like transistors is >>kT/q, eg. ~ 40kT/q

or about ~1Volt

"In addition, power is needed primarily todrive the various lines and capacitances associated with thesystem. As long as a function is confined to a small area ona wafer, the amount of capacitance which must be driven isdistinctly limited. In fact, shrinking dimensions on an integratedstructure makes it possible to operate the structure athigher speed for the same power per unit area."

p. 114

10µm

1µm

100nm

10nm

Moore's Law

1960 1980 2000

Crit

ical

D

imen

sion

2020 2040 2060Year

Tech

nolo

gy G

ap

Gates only

Gates including wires

107

105

102

1

0.1

104

106

10

108

103

Ene

rgy

per B

it fu

nctio

n (k

T)

The other , for energy per bit function

Shoorideh and Yablonovitch, UCLA 2006

Transistor Measurements by Robert Chau, Intel

nano-transformerνh

~1eV

A low-voltage technology, or an impedance matching device,needs to be invented/discovered at the Nano-scale:

transistor amplifier with steeper sub-threshold slope

photo-diode

+ ++

-

+VG

MEM's switch

Cryo-ElectronicskT/q~q/C

Cu

Cu

solid electrolyte

Electro-Chemical Switch

giant magneto-resistancespintronics

+

•TFET's•Negative Capacitance Gates

--V2O5 metal-insulator transition

Theme 1 ‐ Nanoelectronics: Solid‐State Milli‐Volt Switching

An amplifying transistor as a voltage matching device:Small voltage inLarge voltage out

in

outAmplification of weak signals has an energy cost!Amplification of weak signals has a speed penalty!

Gate Voltage

Cur

rent

Vg

ln{I}

steeper sub-threshold

slope

The Zener Diode:

EFc

EFv

band

to b

and

tunn

elin

g

Bias Voltage

Diff

usio

n cu

rren

t

Cur

rent

EF

band

to b

and

tunn

elin

g

Bias Voltage

Diff

usio

n cu

rren

t

Sharp Step

Cur

rent

The Esaki Diode:

The Backward Diode as a Switch:

EFc

EFv

band

to b

and

tunn

elin

g

Bias Voltage

Diff

usio

n cu

rren

t

Cur

rent

Sharp Step

The Backward Diode:These have been routinely made in Ge homo-junctions,since the 1960's.

• Modulate the Tunneling Barrier

• Density of States Switch

2 Ways to Obtain Steepness

The sub‐threshold slope for tunneling dependson the steepness of

the band‐edges:

All The CasesN

IP

Z

I

ZP

N

YI P

N

Z

NI

P

Z

IP

N

ZLZ,i

ZIP

X

N

NP

Z

IP

N

Z

N

IP

Z

X

24

I

ZP

N

IP

N

ZLZ,i

IP

N

Z

)(***2 32

*232 ETEVmeJ ZiOLDD

r

hπ=−

)(** ,,32,22 ETEEemJ fZiZAreaDDr

hπ=−

)(*42

2

32

*333 Ε=−

r

hT

VmeJ OLDD

π

I

VG

2OLVI ∝

I

VG

ConstantI ∝

I

VG

NI

P

Z

NI

P

Z

NP

Z

)(**2*210 ETE

heI ZiDD

r=−

)(*)(***4*2,,00 fifZiZDD EEETEE

heI −=− δ

r

)(**2 2Point,11 Ε=−

rTV

heJ OLDD

I

VG

ConstantI ∝

I

VG

I

VG

YI P

N

Z

ZIP

X

N

N

IP

Z

X

)(***222

2/321 ETVEmeJ OLZiDD

r

hπ=−

)(1**2,,22

2/1,11 ET

VEEmeJ

OLfZiZEdgeDD

r

hπ=−

)(*3

2 2/322

2/5Edge,22 ETVmeJ OLDD

r

hπ=−

I

VG

2/3OLVI ∝

I

VG

OLVI ∝

VG

OLVI 1∝

EC

OFF

material 2(AlGaSb)

oxide

gate metal

quantum well 1 (I

nAs)

EF

EV

EF

EC

ON

EF

EF

EV

oxide

gate metal

quantum well 1 (I

nAs)

material 2(AlGaSb)

EC

SHARPLYOFF

material 2(AlGaSb)

oxide

gate metal

quantum well 1 (InA

s)

EF

EV

EF

CDEP

CQW

COX

z

Theme 1:Key Scientific Questions (Kickoff Meeting 2010)

• New examples of Type III Energy band offsets need to be discovered.

• Fundamental band edge abruptness is very poorly understood.

• We need to concentrate on 2d/2d pn junctions

• Do we want to go all the way to monolayer/monolayer pn junctions?

• Will that guarantee reproducible thresholds?

nano-transformerνh

~1eV



photo-diode

+ ++

-

+VG

MEM's switch


Cu

Cu

solid electrolyte



+



Theme 2 ‐ NanoMechanics: Solid‐State Milli‐Volt Switching

Why Mechanical Switches?

• Relays have zero off‐state leakage zero static energy

Source

DrainGate

Air gap

tgap tdimple

32

3-Terminal Relay

• Relays switch on/off abruptly allows for aggressive VDD scaling (ultra‐low dynamic energy)

Measured I-V

Gate Voltage

Dra

in C

urre

nt

S≈0.1mV/dec

VPIVPO

Relay On‐State Resistance

• ~1K Ohm resistance is acceptable for performance.Formation of metal‐metal bonds in the on state is not necessary!

• Physical contact can be avoided altogether, to eliminate surface adhesion, with a deformable dielectric:

33

tunneling current

• Electrodes can be coated to improve reliability:

dielectric

Tunneling Nanoswitch

Advantages:• ease of fabrication and packaging

• better device reliability

Device Operating Principle:• Electrostatic actuation of electrode • Conduction via tunneling

• nanoconductors embedded in a deformable matrix

7.7

mV

/ D

ecad

e

Pull-In/Pull-Out

Bulovic / Lang (MIT)

Tunneling Micro-Electro-Mechanical Systems:

Double Win:

1. By never making direct contact, we don't pay the energy price of theinterfacial energy.

2. By never making direct contact, the reliability issues are greatly eased.

This comes at the price of higher resistance, but we know the wires in chips have a

characteristic impedance ~1000 Ohms.

This is achievable by tunneling without direct contact!

nano-transformerνh

~1eV



photo-diode

+ ++

-

+VG

MEM's switch


Cu

Cu

solid electrolyte



+



Theme 4 – NanoPhotonics for Ultra‐Low Energy Communication

Ultra-sensitive Floating Gate photodetector:

Eliminate wire capacitance between photodetector and amplifierTransistor with a floating Ge-islandPhotonic crystal cavity with 1000×efficiency improvement.

SiO2

Silicon

Drain

Source

n-Si n-Si

Ge islandn-Si channel

Reflectors integrated with SOI waveguides to create a transverse cavity

incident light

Source Drain

SiO2

Silicon

n-Sih+h+

e- e-

Photons modulate depletion widthGe

-1000

-800

-600

-400

-200

0

200

400

600

800

1000

Volta

ge (µ

V)

0 100 200 300 400 500

Time (ps)

40psec

39

nano-transformerνh

~1eV



photo-diode

+ ++

-

+VG

MEM's switch


Cu

Cu

solid electrolyte



+



Theme 3 – NanoMagnetics: Surmounting the Landauer Limit

41

Fundamental Limits of Computing

Charles BennettRolf Landauer

Von Neumann-Landauer limit (1961):Energy lost in a logic operation in which 1 bit is lost is E ≥ kT ln 2

John von Neumann

Bennett (1973):Logical Reversibility of Computation

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