Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum...

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NOEL Extending CMOS: Quantum Functional Circuits Using Si - Based Resonant Interband Tunnel Diodes Paul R Berger Department of Electrical and Computer Engineering Department of Physics Ohio State University Columbus, OH 43220 USA Berger (Si - Based RITDs) September 20, 2017

Transcript of Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum...

Page 1: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

NOEL

Extending CMOS:

Quantum Functional Circuits

Using Si-Based

Resonant Interband Tunnel Diodes

Paul R Berger

Department of Electrical and Computer Engineering

Department of Physics

Ohio State University

Columbus, OH 43220 USA

Berger (Si-Based RITDs) September 20, 2017

Page 2: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

NOEL

Collaborators

Naval Research Laboratory

Glenn Jernigan, Phillip E. Thompson, Karl Hobart,

and Brad Weaver

IMEC

Roger Loo, Ngoc Duy Nguyen (now Univ-Liege), Shotaro Takeuchi

(now Covalent Silicon), and Matty Caymax

Rochester Institute of Technology

Sean L. Rommel, Santosh K. Kurinec, and Karl D. Hirschman

University of California, Riverside

Roger Lake

NIST, Gaithersberg

David Simons

Berger (Si-Based RITDs) September 20, 2017

Page 3: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

NOEL

Students

Current Graduate Students & Researchers

Dr. Tyler Growden & Parastou Fakhimi

Former Graduate Students

Ms. Anisha Ramesh (Ph.D. 2012)

Si-Young Park (Master’s Thesis 2006, Ph.D. 2009)

Ronghua Yu (Ph.D. 2007)

Sung-Yong Chung (Master's Thesis 2002, Ph.D. 2005)

Sandro Di Giacomo (Master's Thesis 2005)

Niu Jin (Master's Thesis 2001, Ph.D. 2004)

Anthony Rice (Master's Thesis 2003)

Sean L. Rommel (Ph.D. 2000)

Berger (Si-Based RITDs) September 20, 2017

Page 4: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Present Day

CMOS Challenges

Page 5: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department
Page 6: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department
Page 7: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Moore’s law

Page 8: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Motivation: Extending CMOS?

2000 2002 2004 2006 2008 2010 2012 2014 2016 2018

1

10

100

1000

1E-3

0.01

0.1

22283545607090130

0.002

Source: 2001 ITRS Roadmap

Co

st

(µcen

ts/t

ran

sis

tor)

Production Year

0.347

En

erg

y p

er

Sw

itch

(fJ

/Devic

e)

1.66

107

Year

Node Size (nm)

No Known Solutions

NOEL

CMOS cannot be scaled indefinitely.

Solutions: either replace or augment scaled CMOS

Tunnel diodes married with CMOS offer enhancements

Berger (Si-Based RITDs) September 20, 2017

Page 9: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Intel’s Core i7

6T SRAM cache memory dominates footprint

and power consumption, operates about 1 volt

(→ 8T SRAM)

Power consumption related to voltage squared

(~1 volt state-of-the-art)

NOEL Berger (Si-Based RITDs) September 20, 2017

Page 10: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Let’s Enter the

Quantum World

Page 11: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Cu

rre

nt

Voltage

“N-shaped”

negative differential

resistance (NDR)

• How to characterize tunnel diode?

– Peak-to-valley current ratio

PVCR = Ip / Iv

– Peak current density

Jp = Ip / Area

– Speed index

s = Jp / Cj

• Why use TD with transistors?

– Increases circuit speed

– Reduces circuit complexity

– Lowers circuit power

– Simple integration with transistor

Introduction to Advantages of

Tunnel Diodes

NOEL

Ip

Iv

Berger (Si-Based RITDs) September 20, 2017

Page 12: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Three Interband TD Current Components

From Sze, Physics of Semiconductor Devices, pg. 517 (1981).

Desired: optimize

structure for efficient

quantum mechanical

tunneling

Undesired: excess

current comprised

partially of defect related

tunneling

Thermal diffusion

current eventually takes

over at higher biasesBasic TD Figure-of-Merit

• Peak-to-valley current ratio (PVCR) = Ip/Iv

• Peak current density (PCD or Jp )= Ip/A, where A is the diode area

NOEL Berger (Si-Based RITDs) September 20, 2017

Page 13: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

• Band-to-band tunneling current

– PVCR, PCD, and speed

• Excess tunneling current

– PVCR and Standby power dissipation

• Thermal diffusion current

)(24/exp2/32/1 VVqEmW big

png

xx VVeeVE

eWD (6.0

2exp

5.0

From Sze

Goal: Increase band-to-band current and minimize excess current.

Physics Based Model for RITDs

1 kTqV

oth eJJ

Band-to-band tunneling current

Excess current

Thermal current

Cu

rren

t

Voltage

NOEL Berger (Si-Based RITDs) September 20, 2017

Page 14: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Excess Current of an Esaki DiodeFigure adapted from Sze, Physics of Semiconductor Devices, pg. 528 (1981).

•Excess current limits PVCR.

•Excess current is a

tunneling phenomena via

defect or midgap states

For more info see Chynoweth et al.,

Phys. Rev., vol. 121, p. 684, (1961).

NOEL Berger (Si-Based RITDs) September 20, 2017

Page 15: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

The Opportunity

Page 16: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Opportunity: Tunnel Diode Memory

• One Transistor 2-Tunnel Diode SRAM (1T TSRAM)

• Robust operation at low voltages

• Refresh-free – Low active and standby power Consumption

• J. P. A. van der Wagt, A. C. Seabaugh, and E. A. Beam, III, “RTD/HFET low standby power SRAM

gain cell,” IEEE Electron Dev. Lett. 19, pp. 7-9 (1998).

• J. P. A. van der Wagt, “Tunneling-Based SRAM,” Proc. of IEEE, 87, pp. 571-595 (1999).

NOEL Berger (Si-Based RITDs) September 20, 2017

Page 17: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

NOEL

2005 ITRS – Emerging Research Devices

• Monolithic Integration of Si-based tunnel

diodes with Si-based transistors

Berger (Si-Based RITDs) September 20, 2017

Page 18: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

NOEL 2005 ITRS – Emerging Research Devices

Page 19: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

NOEL

More computational power per unit area

Fewer devices required

Faster circuits and systems

Reduced power consumption

The Payoff: TDs Integrated with Transistors

Result: Extension of CMOS if a

Si-Based TD is available that is

compatible with CMOS!

Berger (Si-Based RITDs) September 20, 2017

Page 20: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Now Let’s Apply Quantum

Mechanics

Page 21: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Solid State Electronic Devices, Seventh EditionBen G. Streetman | Sanjay Kumar Banerjee

Copyright ©2015, 2006 by Pearson Education, Inc.All rights reserved.

Figure 3–13 Energy band discontinuities for a thin layer of GaAs sandwiched between layers of wider band gap AIGaAs. In this case, the GaAs region is so thin that quantum states are formed in the valence and conduction bands. Electrons in the GaAs conduction band reside on “particle in a potential well” states such as E1 shown here, rather than in the usual conduction band states. Holes in the quantum well occupy similar discrete states, such as Eh.

Quantum well

Page 22: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Solid State Electronic Devices, Seventh EditionBen G. Streetman | Sanjay Kumar Banerjee

Copyright ©2015, 2006 by Pearson Education, Inc.All rights reserved.

Figure 2–6 Quantum mechanical tunneling: (a) potential barrier of height V0 and thickness W; (b) probability density for an electron with energy E < V0, indicating a nonzero value of the wavefunction beyond the barrier.

Tennis Ball

“tunnels” through

barrier

Page 23: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Basic Physics: Esaki Tunnel Diode

(Interband)

Degenerate Doping Required – Difficult with conventional epitaxy

For more info see L. Esaki, “New phenomenon in narrow Germanium p-n junctions,” Phys. Rev., vol. 109, p. 603, 1958.

V

V

V

I I I I

V

I

(a) (b) (d) (e) (f)

VV

V V

PeakTunneling current

Excess current

Thermal diffusion current

p(E)

EE

n(E)

I

(c)

V

p(E)

EE

n(E)

V

p(E)

E

n(E)

n(E)

p(E)p(E)

E

E

E

n(E)

n(E) p(E)

EE

Tunneling current

V

E

E

Page 24: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Prior Art: Lack of Si-Based TDs that can be Monolithically

Integrated with Si transistors

Ge Esaki Diode Si Esaki Diode

• Vintage 1960’s alloy technology prevents large-scale batch processing

• Discrete Esaki diodes are ideal for niche applications.

• However the alloy process does not lend itself to an integrated circuit.

Page 25: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Basic Physics: Resonant

Tunneling Diode (Intraband)

Large Band Offset Required

Si/SiGe heterojunction has limited band offset

without a thick relaxed buffer

Alternative barriers (i.e. SiO2) present difficult

heteroepitaxy of single crystal Si quantum well

atop amorphous barrier

For more info see L. L. Chang, L. Esaki

and R. Tsu, “Resonant tunneling in

semiconductor double barriers,” Appl.

Phys. Lett., vol. 24, pp. 593-595, 1974.

V

(c) (d)(a)

V V

intrinsic

I

(b)

V

I

V

I

V

I

V

emitter collectorTunneling current Excess current Thermal diffusion current

Page 26: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

I I I

V

I

(a) (b) (c) (d)

V V V

V

V

V

n -delta doping

p- delta doping

Tunneling current Excess current Thermal diffusion current

Basic Physics: Resonant Interband

Tunneling Diode

δ-doping to form quantum wells;

eliminates need for degenerately

doped junctions

For more info see M. Sweeny and J. Xu,

“Resonant interband tunnel diodes,” Appl. Phys.

Lett., vol. 54, pp. 546-548, 1989.

Page 27: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

100 nm n+ Si

Sb-delta doping plane

1 nm undoped Si

4 nm undoped Si0.5Ge0.5

1 nm undoped Si

B-delta doping plane

100 nm p+Si

p+ Si substrate

MBE Heterostructure

• Low growth temperature (320 oC)

• CMOS process compatibility

World’s First Si-Based Resonant Interband

Tunnel Diode (1998)

“Room Temperature Operation of Epitaxially Grown

Si/Si0.5Ge0.5/Si Resonant Interband Tunneling Diodes,"

Sean L. Rommel, Thomas E. Dillon, M. W. Dashiell, H.

Feng, J. Kolodzey, Paul R. Berger, Phillip E.

Thompson, Karl D. Hobart, Roger Lake, Alan C.

Seabaugh, Gerhard Klimeck, and Daniel K. Blanks,

Appl. Phys. Lett., 73, pp. 2191-2193 (1998).

0.0 0.2 0.4 0.6 0.80

5

10

300 K

Peak to Valley Current Ratio : 1.4

Peak Current Density : 2.8 kA/cm2

NRL 80424.2

4 nm i-SiGe spacer

1 nm -dope offsets

700 0C, 1 min anneal

18 m diameter

6 adjacent devices

Cu

rre

nt

(mA

)

Voltage (V)

NOEL

Page 28: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Si/Si0.6Ge0.4/Si RITDs

Grown at 320 oC

High Peak-to-Valley Current Ratios

100 nm n+ Si

P -doping plane

4 nm undoped Si

4 nm undoped Si0.6Ge0.4

B -doping plane

1 nm p+ Si0.6Ge0.4

100 nm p+ Si

p+ Si substrate

MBE Heterostructure

Tu

nn

el

Barr

ier

Greater defect annihilation leads to less excess

current in valley region and therefore higher PVCRs

0.0 0.2 0.4 0.6 0.8 1.00

1

2

3

4

5

6

7

OSU/NRL RITDs (#050322.2)

800 oC, 1-min anneal

etched by HBr

PVCR: 4.03

PCD: 142 A/cm2

Cu

rre

nt (m

A)

Voltage (V)

NOEL

-1.5

-1

-0.5

0

0.5

1

45 50 55 60

Ene

rgy

(eV

)

Position (nm)

V = 0.4VX

zX

xy

HHLH

SO

|Xxy

>

|Xz>

|HH>|LH> Courtesy

R. Lake (UC

Riverside)

Berger (Si-Based RITDs) September 20, 2017

Page 29: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

NOEL

First Si-Based Resonant Interband Tunnel Diodes

Front page of the Wall

Street Journal

(October 1, 1998).

Approach

EC

(eV)

Upper

Barrier

Crystalline

Quantum

Well

Crystalline

Lower

Barrier

Crystalline

Production

PotentialStatus

SiO2/a-Si/SiO2 3.2 No No No High Abandoned - High scattering in quantum,

no room temperature PVR

CaF2/Si/CaF2 2 Yes Yes Yes Low Abandoned - Tendency for island growth,

defect-assisted transport below 10 nm

ZnS/Si/ZnS 1 Yes Yes Yes Med. ZnS on Si growth established, Si quantum well

growth under study

SiO2/Si/SiO2

Lateral overgrowth

3.2 No Yes No Med. Process for forming oxide islands established,

overgrowth process under development

ZnS/Si/ZnS

Lateral overgrowth

1 Yes Yes Yes Med. ZnS islands have been prepared for first

overgrowth experiments

SiO2/SiGe(C)/SiO2

Lateral overgrowth

3.2 No Yes No Med. Oxide islands have been prepared for first

overgrowth experiments

SSii//SSiiGGee

rreessoonnaanntt iinntteerrbbaanndd

ttuunnnneell ddiiooddee

-- -- -- -- HHiigghh WWoorrlldd’’ss ffiirrsstt ddeemmoonnssttrraattiioonn oonn SSii;;

rroooomm tteemmppeerraattuurree ppeeaakk--ttoo--vvaalllleeyy

ccuurrrreenntt rraattiioo ooff 11..66

980505

A paradigm shift from other approaches was spearheaded

by a team of researchers lead by Berger (then at the

University of Delaware), Naval Research Laboratory and

Raytheon Systems.

• DARPA Award of Excellence (1998)

• Late News at International Electron Devices Meeting

(1998)

• Best Science/Engineering Dissertation (2000)

• Special Invitation to 2003 ITRS Meeting

• IEEE Fellow (2011)

Berger (Si-Based RITDs) September 20, 2017

Page 30: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

5 Key Features of the Original RITD Design

A pair of δ-doping planes of B and P (or Sb) provide highly degeneratedoping levels which can confine quantum states in potential energy wells.The gap between δ-doping planes is assumed the tunneling distance.

An intrinsic layer is used as the central tunneling spacer, which reducescarrier scattering. Both Si and Si/Si1-xGex composite spacers have beenexplored. The addition of Ge provides greater momentum mixing andtherefore higher current densities.

Fixed offsets between the δ-doping planes and the tunneling spacerwere introduced in some SiGe designs to minimize the outdiffusion ofdopants and impurity accumulation into the central tunneling spacer.

Samples were epitaxially grown by low-temperature molecular beamepitaxy (LT-MBE) to allow for greater dopant incorporation and abruptinterfaces minimizing segregation and diffusion.

Short post growth rapid thermal annealing (RTA) heat treatments wereintroduced to reduce the point defect density associated with lowtemperature growth. Diffusion during annealing may decrease the spacerthickness and reduce as-grown δ-doping levels.

“Si-Based Resonant Interband Tunneling Diodes,” Paul R. Berger, Sean L. Rommel, Phillip E.

Thompson, Karl D. Hobart, and Roger Lake, [Issued on October 12, 2004, U. S. Patent #6,803,598].

“Method of Making Interband Tunneling Diodes,” Paul R. Berger, Sean L. Rommel, Phillip E.

Thompson, Karl D. Hobart, and Roger Lake, (U. S. Patent #7,303,969).

NOEL Berger (Si-Based RITDs) September 20, 2017

Page 31: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Isothermal Annealing Effects with Cladding

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

25

50

75

100

125

150

175

200

225

250

275

300

325

350

RITD 042 CLAD

PVCR = 3.6

RITD 042

PVCR = 3.0

RITD 141

PVCR = 1

Cu

rre

nt

De

nsity (

A/c

m2)

Voltage (V)

“Diffusion Barrier Cladding in Si/SiGe Resonant

Interband Tunneling Diodes And Their Patterned

Growth on PMOS Source/Drain Regions,” Niu Jin,

Sung-Yong Chung, Anthony T. Rice, Paul R.

Berger, Phillip E. Thompson, Cristian Rivas,

Roger Lake, Stephen Sudirgo, Jeremy J.

Kempisty, Branislav Curanovic, Sean L. Rommel,

Karl D. Hirschman, Santosh K. Kurinec, Peter H.

Chi and David S. Simons, Special Issue on

“Nanoelectronics” in IEEE Trans. Elect. Dev., vol.

50, pp. 1876-1884 (September 2003).

Diffusion barrier cladding

surrounding the δ-doping

spike raises the process

thermal budget and allows for

greater defect annihilation

before interdiffusion becomes

serious

Annealed 825 oC for 1 minute

NOEL Berger (Si-Based RITDs) September 20, 2017

Page 32: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Very High Peak Current Densities

100 nm n+ Si

P -doping plane

1 nm undoped Si

2 nm undoped Si0.6Ge0.4

B -doping plane

1 nm undoped Si0.6Ge0.4

100 nm p+ Si

p+ Si substrate

Tu

nn

el

Barr

ier

0.0 0.2 0.4 0.6 0.8 1.00

50

100

150

Measured RITDExtracted Intrinsic RITD

Voltage (V)

OSU/NRL Si/SiGe RITD

(2nm Si0.6

Ge0.4

/1nm Si)

Sharpened P peak

5 m diameter diode

575oC, 1 min anneal

Cu

rre

nt

De

nsity (

kA

/cm

2)

Si/Si0.6Ge0.4/Si RITDs

Grown at 320 oC

By reducing tunnel barrier, over 150 kA/cm2 current density!

High current densities valuable for fast switching and RF Mixed Signals

“151 kA/cm2 Peak Current Densities in Si/SiGe

Resonant Interband Tunneling Diodes for High-

Power Mixed-Signal Applications,” Niu Jin, Sung-

Yong Chung, Anthony T. Rice, Paul R. Berger,

Ronghua Yu, Phillip E. Thompson, and Roger

Lake., Appl. Phys. Lett., 83, 3308 (2003).

NOEL Berger (Si-Based RITDs) September 20, 2017

Page 33: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Tailorable Peak Current Densities

Current densities can be

engineered over ~8 orders of

magnitude by controlling RITD

spacer thickness between the δ-

doping pair from 1 nm up to 16 nm.

By widening spacer, below 20 mA/cm2 current density!

Low current densities valuable for memory and low power consumption

0.0 0.2 0.4 0.6 0.8 1.010

-4

10-3

10-2

10-1

100

101

102

103

104

15 nm

14 nm

825oC annealed, 1 min

16 nm

12 nm

10 nm

8 nm

Cu

rre

nt D

en

sity (

A/c

m2)

Voltage (V)

NOEL

0 2 4 6 8 10 12 14 1610

-2

10-1

100

101

102

103

104

105

Pe

ak C

urr

en

t D

en

sity (

A/c

m2)

Spacer Thickness (nm)

Red data points

indicated occur at

maximum PVCRMixed signal

Logic

Memory

Berger (Si-Based RITDs) September 20, 2017

Page 34: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Results highlighted here demonstrate the highest reported peak current density

for Si-based interband tunnel diodes that is 3 times larger than the previous world

record. A high current density is needed to generate large amounts of microwave

power output for radio transmission in small distributed sensor networks

0.0 0.2 0.4 0.6 0.8 1.00

50

100

150

Measured RITDExtracted Intrinsic RITD

Voltage (V)

OSU/NRL Si/SiGe RITD

(2nm Si0.6

Ge0.4

/1nm Si)

Sharpened P peak

5 m diameter diode

575oC, 1 min anneal

Cu

rre

nt

De

nsity (

kA

/cm

2)

Requirement for Memory or Logic Function ( PVCR ≥ 2 )

Requ

irem

en

t for H

igh

sp

ee

d o

r Mix

ed

-Sig

na

l

Circ

uitry

( Jp

>1

0 k

A/c

m2

)

1 2 3 4 5 6

100

1k

10k

100k

RTA/Esaki

(Wang, 2003)

CMOS/RITD

(Sudirgo, 2003)

Si/SiGe RITD (Jin-APL, 2003)

SiGe RITD

(Rommel-APL,

1998)

Esaki Diode

(Dashiell, 2000)

SiGe RITD

(Jin-Eastman,

2002)

SiGe RITD

(Rommel-IEDM

1998)

RITD (Duschl, 2001)

Si-only RITD (Rommel-EDL, 1999)

Esaki Diode

(Jorke, 1993)

Pe

ak

Cu

rre

nt

De

nsi

ty (

A/c

m2)

Peak-to-Valley Ratio (PVCR)

RITD (Duschl, 2000)

Solid circles () indicate prior work by Berger group,

open squares () indicate prior work by other groups,

and stars (*) indicate recent work by Berger group.

RF Mixed Signal Applications Enabled

“151 kA/cm2 Peak Current Densities in

Si/SiGe Resonant Interband Tunneling

Diodes for High-Power Mixed-Signal

Applications,” Niu Jin, Sung-Yong Chung,

Anthony T. Rice, Paul R. Berger, Ronghua

Yu, Phillip E. Thompson, and Roger

Lake., Appl. Phys. Lett., 83, 3308 (2003).

NOEL Berger (Si-Based RITDs) September 20, 2017

Page 35: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Microwave Performance of RITDs

STRUCTURE Uniqueness

• Additional P -doped layer wasinserted for better ohmic contact.

• Ni silicide was formed.

• Minimum space thickness (2.5 nm)with the highest Ge fraction (55 %)was tried.

• 218 kA/cm2 peak current density.

• 20.2 GHz cutoff frequency.

• 35.9 mV/ps of speed index.

P -doping plane

B -doping plane

P -doping plane

1 nm undoped Si

1 nm p+ Si0.45Ge0.55

p Si Substrate (3000-8500 ·cm)

1.5 nm undoped Si0.45Ge0.55

104 nm n+ Si

5 nm n+ Si

264 nm p+ Si

NOEL Berger (Si-Based RITDs) September 20, 2017

Page 36: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Ground

Signal

Ground

Air bridge

DUT

Device Fabrication

For RF measurement

• 1 metal & 2 etching processes havebeen developed, resulting in 0.34m2 sized RITDs.

• Air-bridge is formed to isolate aactive device from huge pad.

• Ni silicidation through P -dopedquantum well by rapid thermalsintering at 430 oC for 30 seconds,resulting in a specific contactresistivity of 5.3×10-7 -cm2, whichis extracted from RF measurement.

Metal (Signal)Metal (Ground)

Forward biased RITD under test

p- Si substrate (3000~8000 Ω-cm)

p++

n++n++

p++

Reverse biased parasitic RITD

NOEL Berger (Si-Based RITDs) September 20, 2017

Page 37: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

1 2 3 4 5 610m

100m

1

10

100

1k

10k

100k

1M

SiGe ITD

(Stoffel, 2005)

Si Esaki Diode

(Oehme, 2010)

SiGe RITD, TED 2006

SiGe RITD, EL 2006

SiGe RITD, EDL 2006

RITD

(Duschl, 1999)

RITD (Duschl, 2000)

Esaki Diode

(Dashiell, 2000)

SiGe RITD

(TED, 2005)

SiGe RITD (APL 2003)

SiGe RITD

(APL, 1998)SiGe RITD

(IEEE-TED, 2003)

SiGe RITD

(IEDM, 1998)

Si-only RITD

(EDL, 1999)

Esaki Diode

(Jorke, 1993)

Pe

ak C

urr

en

t D

en

sity (

A/c

m2)

Peak-to-Valley Ratio (PVCR)

Si-based Interband Tunnel Diode

Technology (PCD & PVCR)

Technology Availability

PVCR up to 4

PCD: 20 mA/cm2 to 218 kA/cm2

“Si/SiGe Resonant Interband Tunnel

Diode with fr0 20.2 GHz and Peak Current

Density 218 kA/cm2 for K-band Mixed-

Signal Applications,” Sung-Yong Chung,

Ronghua Yu, Niu Jin, Si-Young Park,

Paul R. Berger, and Phillip E. Thompson,

IEEE Electron Device Letters 27, pp. 364-

367 (May 2006).

NOEL Berger (Si-Based RITDs) September 20, 2017

Page 38: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Si-based Interband Tunnel

Diode Technology (Speed)

0.1 1 10 100 10000.1

1

10

100

0.1

1

10

100 Cut-off freq.

Peak Current Density (JP, kA/cm

2)

Speed Index (

mV

/ps)

Cut-

off fre

quency

(GH

z) Chung, EDL 2006

Jin, 2005

Jin, 2005

Yan, 2004

Dashiell, 2002

Auer, 2001

Speed Index

Technology Availability

fT: up to 20.2 GHz

Switching Speed: ~ 36 mV/ps

“Si/SiGe Resonant Interband Tunnel

Diode with fr0 20.2 GHz and Peak Current

Density 218 kA/cm2 for K-band Mixed-

Signal Applications,” Sung-Yong Chung,

Ronghua Yu, Niu Jin, Si-Young Park,

Paul R. Berger, and Phillip E. Thompson,

IEEE Electron Device Letters 27, pp. 364-

367 (May 2006).

NOEL Berger (Si-Based RITDs) September 20, 2017

Page 39: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

260 nm p+ Si0.8Ge0.2

4 nm i Si0.4Ge0.6 spacer

Si0.8Ge0.2 substrate

1 nm p+ Si0.4Ge0.6

2 nm i Si spacer

100 nm n+ Si0.8Ge0.2

B δ-doping layer

P δ-doping layer

2 nm n+ Si

17.5 nm Cap Si

260 nm p+ Si0.8Ge0.2

4 nm i Si0.4Ge0.6 spacer

1 nm p+ Si0.4Ge0.6

100 nm n+ Si0.8Ge0.2

B δ-doping layer

P δ-doping layer

2 nm i Si0.8Ge0.2 spacer

Si0.8Ge0.2 substrate

17.5 nm Cap Si

Tensile Strain on Virtual SiGe

• SiGe virtual substrates utilized for higher Ge content in the spacer toincrease tunneling probability

• Thin tensilely strained Si layer cladding around P δ-doping spike acting asa P diffusion inhibitor

Structure ‘A’ Structure ‘B’

NOEL Berger (Si-Based RITDs) September 20, 2017

“Strain Engineered

Si/SiGe Resonant

Interband Tunneling

Diodes Grown on

Si0.8Ge0.2 Virtual

Substrates,” N. Jin

et.al., IEEE EDL, 29,

599 (2008)

Page 40: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

900 1000 1100 1200

-1

0

1

260nm

Si 0

.8G

e0

.2

100nm

Si 0

.8G

e0

.2

1nm

Si 0

.4G

e0

.6

4nm

Si 0

.4G

e0

.6

2nm

Si 0

.8G

e0

.2

B

-dopin

g

P

-dopin

g

Si 0

.8G

e0

.2 S

ubstr

ate

Surf

ace

EV

EC

Ene

rgy (

eV

)

Depth (A)

EF

900 1000 1100 1200

-1

0

1

100nm

Si 0

.8G

e0

.2

260nm

Si 0

.8G

e0

.2

2nm

Si

2nm

Si

1nm

Si 0

.4G

e0

.6

4nm

Si 0

.4G

e0

.6

B

-dopin

g

P

-dopin

g

Si 0

.8G

e0

.2 S

ubstr

ate

Surf

ace

EV

EF

Ene

rgy (

eV

)Depth (A)

EC

Deepened P-well

Tensile Strain on Virtual SiGe

Structure ‘B’Structure ‘A’

“Strain Engineered Si/SiGe Resonant Interband Tunneling Diodes Grown on Si0.8Ge0.2 Virtual Substrates,”

N. Jin et.al., IEEE EDL, 29, 599 (2008)

NOEL Berger (Si-Based RITDs) September 20, 2017

Page 41: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

750 775 800 825 8501.0

1.5

2.0

2.5

3.0

Annealing Temperature (oC)

PVCR: Structure B (P-cladding)

PVCR: Structure A (control)

PV

CR

0.0 0.2 0.4 0.6 0.80

30

60

90

120

Voltage (V)

Cu

rre

nt

De

nsity (

A/c

m2)

Structure A,

800 oC annealed

Structure B,

835 oC annealed

• Increase in optimal annealing temperature due to reduced P diffusion• 1.8x increase in PVCR

Tensile Strain on Virtual SiGe

“Strain Engineered Si/SiGe Resonant Interband Tunneling Diodes Grown on Si0.8Ge0.2 Virtual Substrates,” N. Jin et.al.,

IEEE EDL, 29, 599 (2008)

NOEL Berger (Si-Based RITDs) September 20, 2017

Page 42: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

260 nm p+ Si0.8Ge0.2

4 nm i Si0.5Ge0.5 spacer

Si0.8Ge0.2 substrate

1 nm p+ Si0.5Ge0.5

1 nm i Si spacer

2 nm p+ Si

100 nm n+ Si0.8Ge0.2

2 nm n+ Si0.5Ge0.5

B delta doping layer

P delta doping layer

2 nm n+ Si

260 nm p+ Si0.8Ge0.2

4 nm i Si0.5Ge0.5 spacer

Si0.8Ge0.2 substrate

1 nm p+ Si0.5Ge0.5

1 nm i Si spacer

100 nm n+ Si0.8Ge0.2

B delta doping layer

P delta doping layer

2 nm n+ Si

Outside Barriers

• Tensilely strained p-type and compressively strained Si0.5Ge0.5 n-type added.

NOEL Berger (Si-Based RITDs) September 20, 2017

“Strain Engineered

Si/SiGe Resonant

Interband Tunneling

Diodes with Outside

Barriers Grown on

Si0.8Ge0.2 Virtual

Substrates,” A. Ramesh

et.al., APL, 93, 102113

(2008).

Page 43: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Outside Barriers

0 5 10 15 20 25 30

-1.0

-0.5

0.0

0.5

1.0

1.5

Ev = 0.2 eV

Ev

EfEne

rgy (

eV

)

Distance (nm)

Ec

Ec = 0.2 eV

0 5 10 15 20 25 30-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Ev = 0.26 eVE

v

Ef

En

erg

y (

eV

)

Distance (nm)

Ec

Ec = 0.28 eV

• Electron and hole quantum well deepened.

“Strain Engineered Si/SiGe Resonant Interband Tunneling Diodes with Outside Barriers Grown on Si0.8Ge0.2 Virtual

Substrates,” A. Ramesh et.al., APL, 93, 102113 (2008).

NOEL Berger (Si-Based RITDs) September 20, 2017

Page 44: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

It is shown that outside barriers can enhance the Jp while reduce the Jv.

The QW is deepened due to the accumulation of bandgap offset (Enhance Jp)

The barrier can block the non-resonant tunneling current (Reduce Jv)

Device Results

800 810 820 830

PV

CR

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4

Annealing Temperature (oC)

PVCR: w/o outside bariers

PVCR: w/ outside barriers

800 810 820 830

0

50

100

150

200

250

300

350

400

Cu

rre

nt

De

nsity(A

/cm

2)

Jp: w/o outside barriers

Jv: w/o outside barriers

Jp: w/ outside barriers

Jv: w/ outside barriers

Annealing Temperature (oC)

“Strain Engineered Si/SiGe Resonant Interband Tunneling Diodes with Outside Barriers Grown on Si0.8Ge0.2 Virtual

Substrates,” A. Ramesh et.al., APL, 93, 102113 (2008).

NOEL Berger (Si-Based RITDs) September 20, 2017

Page 45: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Technology Transfer: RITD

0.0 0.2 0.4 0.6 0.8 1.00

1

2

3

4

5

6

7

OSU/NRL RITDs (#050322.2)

800 oC, 1-min anneal

etched by HBr

PVCR: 4.03

PCD: 142 A/cm2

Cu

rre

nt (m

A)

Voltage (V)

0.0 0.2 0.4 0.6 0.8 1.00

5

10

15

20

25

Si/Si0.6

Ge0.4

CVD RITD

6 nm barrier (Si=2, SiGe=4)

PVCR = 5.21, Jp = 20 A/cm

2

10 m

15 m

30 m

40 m

Cu

rrent D

ensity (

A/c

m2)

Voltage (V)

MBE Prototype CVD Tech Transfer *

* Grown on a standard ASM reactor (200 mm) at IMEC

NOEL Berger (Si-Based RITDs) September 20, 2017

“High 5.2 Peak-to-Valley Current Ratio in Si/SiGe Resonant Interband Tunnel Diodes Grown by Chemical Vapor

Deposition,” A. Ramesh et.al., APL, 100, 092104 (2012).

Page 46: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Fabrication Technology Developed

100 nm p+ Si

100 nm n+ Si

X nm i-Si

Y nm i-Si0.6Ge0.4

1 nm p+ Si0.6Ge0.4

Implanted p+ Si

P -plane

B -plane

X+Y nm i-layer

n-well

n-Si substrate

~~

~~

~~

SiO2

TEOS

p-welln-well

implanted p+ n+ n+

TEOSAl

n+

polyTD TD

NFETBack-to-back

Si/SiGe RITD

~~

• Over 80 major steps

• LOCOS isolation

• Double well technology

• n+ polysilicon gate

• Self-aligned S/D

• Low Temperature Molecular

Beam Epitaxy (NRL)

• Post Growth Rapid Thermal

Anneal (OSU)

• Al(1%Si) Metalization

"NMOS/SiGe Resonant Interband Tunneling Diode Static Random Access Memory," S. Sudirgo,

et al., Proceedings of the Device Research Conference (State College, PA, USA, 2006), p. 265..

Page 47: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

SEM Micrograph Gallery

10 μm

PMOS

NMOS Si/SiGe

RITD

PWord

PBit

NBit

NWord

VSN

Ground

N-Well

Contact

P-Well

Contact 051003.3

4-State CMOS AMV-TSRAM

RITD Load

RITD Drive

NFET

Word

Bit

VSN

VDD

Ground

20 m

Binary 2TD-1T

051003.320 m

Binary 2T-1TD

051003.3

051003.3

VSN

GroundNFET

10 μm

WordBit

VDD

5-State 4TD-1T

"NMOS/SiGe Resonant Interband Tunneling Diode Static Random Access Memory," S. Sudirgo,

et al., Proceedings of the Device Research Conference (State College, PA, USA, 2006), p. 265..

Page 48: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Integrated CMOS and Si/SiGe RITD

-5 -4 -3 -2 -1 0 1 2 3 4 50.0

5.0

10.0

15.0

20.0

25.0

30.0

-2.5V

NFET

3.0V

3.5V

4.0V

4.5V

VG = 5V

-3.0V

-3.5V

-4.0V

-4.5V

|ID

S| (

m)

VDS

(V)

VG = -5V 051003-D4 R3C2

LMask

= 4m

PFET

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.710

0

101

102

1.90

1.90

2.03

1.92

12 nm

10 nm

8 nm

Cu

rren

t D

ensi

ty (

A/c

m2)

Voltage (V)

Integrated Si/SiGe RITDs

051003 D2, D4, D5, D6

6 nm

Device PVCR

6 nm

8 nm

10 nm

12 nm

• Integrated NMOS exhibits a typical VT around 3.0 V.

• Integrated PMOS has VT around -2.65 V.

• Si/SiGe RITDs with various i-layer thicknesses: 6, 8, 10, and 12 nm.

• JP ranges from 10-100 A/cm2, and PVCR up to 2.3.

"NMOS/SiGe Resonant Interband Tunneling Diode Static Random Access Memory," S. Sudirgo,

et al., Proceedings of the Device Research Conference (State College, PA, USA, 2006), p. 265..

Page 49: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

The First Integrated Si/SiGe TSRAM

0.0 0.1 0.2 0.3 0.4 0.5 0.60.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

VDD

=

0.57V

I Dri

ve,

I Lo

ad (

mA

)

VSN

(V)

IDrive

ILoad

0.51003.D4

R3C5 CN1-12

0.13V 0.43V

PVCR = 1.87

JP = 52 A/cm

2

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

0.1

0.2

0.3

0.4

0.5

0.6

0.78V0.57V0.47V

0.36V

VH = 0.59V

0.12V0.13V

0.0V - 1.0V

1.0V - 0.0V

VL

= 0.21V

VS

N (

V)

VDD

(V)

0.51003.D4

R3C5 CN1-12

0.44V

0.2 0.4 0.60.0

0.1

0.2

0.3

0.4

0.5

WH

0.30 V

0.43 V

"1"

Time (sec)

VS

N (

V)

"0" "0"

"1"

0.13 V

0.0

1.0

2.0

3.0 WL SB WL

Word

(V

)

WLWH SBSB

0.0

0.2

0.4

0.6

0.8

1.0

SB

Bit

(V

)

VDD

= 0.57V

• Low voltage operation down to 0.37 V

and %VSWING up to 53.5%.

"NMOS/SiGe Resonant Interband Tunneling Diode Static Random Access Memory," S. Sudirgo,

et al., Proceedings of the Device Research Conference (State College, PA, USA, 2006), p. 265..

Page 50: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

Si-Based RITD Results Summary

•High PVCR (5.2)

•High PCD (≥ 218 kA/cm2)

•Low PCD (≤ 20 mA/cm2)

• Vertically stacked back-to-back RITDs for

symmetric NDR

• Tri-state logic with vertically stacked RITDs

• Low voltage MOBILE latches (CMOS-RITD)

NOEL

Device Optimization Hybrid Circuit Prototyping

Device Integration Monolithic Circuits

•Monolithic integration with CMOS

•Monolithic Integration with SiGe HBTs

•CVD Integration

•Low power/low voltage TSRAM

•Low power/low voltage MOBILE

•Adjustable PVCR (HBT-RITD)

Berger (Si-Based RITDs) September 20, 2017

Page 51: Quantum Functional Circuits (Berger)berger/summ_ritd/2017-OSU-Berger-RITD-update2.pdfQuantum Functional Circuits Using Si-Based Resonant Interband Tunnel Diodes Paul R Berger Department

For Further Reading

Paul R. Berger, Anisha Ramesh “Negative Differential Resistance Devices and Circuits” in

Comprehensive Semiconductor Science and Technology, Elsevier, Volume 5, Chapter 13, pp.

176–241 (2011).

A. C. Seabaugh, B. Brar, T. Broekaert, G. Frazier, and P. van der Wagt, “Resonant tunneling

circuit technology: has it arrived?” 1997 GaAs IC Symposium, pp. 119-122.

A. Seabaugh and R. Lake, “Tunnel diodes,” Encyl. Appl. Phys., vol. 22, pp. 335-359 (1998).

J.P. Sun, G.I. Haddad, P. Mazumder, J.N. Schulman, “Resonant tunneling diodes: Models and

properties,” Proc. of IEEE, vol. 86, pp. 641-661 (1998).

P. Mazumder, S. Kulkarni, Bhattacharya M, J.P. Sun, G.I. Haddad, “Digital circuit applications of

resonant tunneling devices, Proc. IEEE, vol. 86, pp. 664-686 (1998).

J. P. A. van der Wagt, “Tunneling-Based SRAM,” Proc. of IEEE, vol. 87, pp. 571-595 (1999).

A. Seabaugh, B. Brar, T. Broekaert, F. Morris, P. van der Wagt, and G. Frazier, “Resonant-

tunneling mixed-signal circuit technology,” Solid State Electronics, vol. 43 pp. 1355-1365 (1999).

K. Maezawa, T. Akeyoshi, and T. Mizutani, “Flexible and reduced-complexity logic circuits

implemented with resonant tunneling transistors,” International Electron Devices Meeting

Technical Digest, pp. 415-418 (1993).

NOEL Berger (Si-Based RITDs) September 20, 2017