Surface Channel MESFETs on H-Terminated Diamondasdn.net/ngc2011/presentations/conte.pdf•1987:...

S2DEL - Solid State and Diamond Electronics LabROMATRE

Università degli Studi

1/26

Gennaro (Rino) Conte

E. Giovine

A. Bolshakov, V.G. Ralchenko, V. Konov

Surface Channel MESFETs

on H-Terminated Diamond

Nano and Giga Challengesin Electronics, Photonics and Renewable EnergyMoscow - Zelenograd, Russia, September 12-16, 2011



2/26

Outline

Why Diamond ?

Hydrogenated Diamond: 2DHG ?

Technology Issues

DC and RF MESFETs performance

Fast optically triggered switches?

Conclusions



3/26

Wide Band Gap Semiconductors: an overview

MaterialBand gap

Thermal

conductivity

Breakdown

electric field

EBD

Mobility

holes

Carriers sat.

velocity vsat

Dielectric

constant εr

eV W/cmK 106 V/cm cm2/Vs 107 cm/s -

Diamond 5.5 22 10 1900 2.7 5.7

Gallium nitride 3.45 1.3 2.5 130 2.5 8.9

Silicon carbide 3.27 4.9 3.0 50 2.0 9.7

Gallium Arsenide 1.42 0.46 0.4 320 0.8 12.9

Silicon 1.12 1.5 0.3 480 1.0 11.8

Germanium 0.67 0.58 0.1 1900 1.0 16.2

Johnson[a] FoM = (EBD2vsat

2)/(4π2) EBD vsat = Vmax fmax

Keyes[b] FoM = λ (c vsat/4πε0)1/2

λ: thermal conductivity, c: speed of light

a) E. O. Johnson, "Physical Limitations on Frequency and Power Parameters of Transistors," RCA Review, vol. 26, pp. 163-177, 1965.

b) R. W. Keyes, "Figure of Merit for Semiconductors for High Speed Switches," Proc.IEEE, vol. 60, pp. 225-232, 1972.

Why diamond ?



4/26

Si InP GaAs SiC GaN C

JFoM

KFoM(normalized to Si)

Wide Band Gap Semicondutors: an overview

Communications

Satellite

Wireless

stations

Mobile

terminals

Wireless

LAN

Broadcasting

Stations

Radar

Wide Band Gap Semicondutors are the answer for

High-frequency and High-power applications

Why diamond ?



5/26

Diamond samples grown by Chemical Vapor Deposition (CVD) with CH4 + H2

Single Crystal Plates on HPHT (high pressure high temperature) 5x5 mm2 substrate (SCD)

Polycrystalline diamond on 2-4“ Silicon wafers (PCD)

CVD Diamond for Electronics

Ulm University, Germany

Diamond MaterialsFraunhofer Institute IAF in Freiburg, Germany

Delaware Diamond Knives, DDK Inc.Wilgminton, USA

SCD PCD

element six ltdAscot, Berkshire, UK

General Physics Institute RASMoscow (Russia)

Why diamond ?



6/26

• 1982: diamond based PNP transistorJ. Prins, Appl. Phys. Lett. 41

• 1987: boron doped diamond FETM. W. Geis et al., IEEE Elect. Dev. Lett., 8

• 1991: ion-implanted diamond FETC. Zeisse et al., IEEE Elect. Dev. Lett., 12

• 1992: polycrystalline diamond FETA. J. Tessmer, et al., Diamond Relat. Mater., 1

• 1992: delta-doped diamond FETsN. Fujimori, et al., Diamond Relat. Mater., 1

Diamond based transistors history

• 1994: H-terminated diamond based FETH. Kawarada, et al., Appl. Phys. Lett. 65

• 1997-1999: H-terminated diamond FETs improvementsP. Gluche, et al. IEEE Elect. Dev. Lett., 18 (1997), T. Yun, et al. J. Appl. Phys. 82 (1997)

• 1999: results for -doped technologyA. Aleksov, E. Kohn et al., Diamond Relat. Mat. 8

• 2001: RF performances reported for H-terminated Single Crystal DiamondH. Taniuchi, et al., IEEE Elect. Dev. Lett. 22

• 2005: RF Power performances reported for H-terminated Single Crystal DiamondM. Kasu, et al., Elect. Letters, 41

• 2006: best RF performances reported for H-terminated polycrystalline diamondK. Ueda, et al., IEEE Elect. Dev. Lett. 27

• 2008: RF performances achievement for delta-doped diamond technologyA. El-Hajj, et al., Diamond Relat. Mater. 17



7/26

RF Record performances

K. Ueda et al., Diamond FET using high-quality polycrystalline diamond with fT of

45 GHz and fMax of 120 GHz, IEEE Electron Device Letters, 27 (2006) 570.

Polycrystalline Diamond

21 2

12

2

2 2121

21 12 11 22

11 22 21 12

2 2

11 22

1

2

1 1

1 1

'

SMAG K K

S

SH

S S S S

S S S SU

S S

K Rollett s Stability Factor

Figures of Merit



8/26

Plasma assisted Hydrogen termination of CVD Diamond induces p-type conductive channel [a]

a) M.I. Landstrass & K.V. Ravi “The Resistivity of CVD Diamond Films” Appl. Phys. Lett. 55, 975 (1989)

b) F. Maier, M. Riedel, B. Mantel, J. Ristein, L. Ley “Origin of Surface Conductiviy in Diamond” Phys. Rev. Lett. 85, 16 (2000)

c) C. E. Nebel, B. Rezek, A. Zrenner “2D-hole accumulation layer in hydrogen terminated diamond” Phys. Stat. Sol. 201, 11 (2004)

d) V. Chakrapani, J. C . Angus, et al. “Charge Transfer Equilibria between diamond and an acqueous Oxygen Electrochemical redox couple” Science 318 (2007)

e) T. Maki, S. Shikama. M. Komori, et al “Hydrogenating Effect of Single-Crystal Diamond Surface” Jap. J. Appl. Phys. 31 (1992)

• Surface band bending where valence-band electrons transfer into an adsorbate layer: “transfer doping model”[b,c,d]

• Shallow hydrogen induced acceptors[e]

Diamond surface hydrogenationHydrogenated Diamond: 2DHG ?

Electrons from the valence-band diffuse into empty electronic states of the adsorbate layer as long as the chemical

potential µe is lower than the Fermi energy



9/26

10-15

10-14

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

0 5 10 15 20

Co

nd

uctiv

ity (S

/cm)

1000/T (K-1

)

Co

nd

uct

ivit

y (

S/c

m)

Ea= 0.9 eV

Ea= 3 meV


1 cm2, Ag 200 nm

Average Roughness 2-8 nm

H-Terminated Surface

O-Terminated Surface

Hydrogen Termination Analysis

0

5

10

15

20

0 50 100 150 200

Poly-Ra270

Hydrogenated

TLM-Au

Z=150 m

C3-B

C5-B

C14-B

y = 0.084211 + 0.10279x R= 0.99779

RT (

k

Distance, d ( m)

(2RC) (R

Sh/Z)

LT=2.5 m

C=2.5x10

-5 cm

2



10/26

0

20

40

60

80

100

120

140

0 10 20 30 40 50

E6 High Quality SCD

E6 Standard SCD

RAS SCD P14MS

RAS PolyD4

Hall

Mo

bil

ity (

cm

2/V

s)

1000/T (K-1

)

EA=1.6 meV

EA

=1.8 meV

EA=4.1 meV

EA<0.2 meV

1012

1013

1014

0 10 20 30 40 50 60

RAS Polycrystalline D4

RAS SCD P14MS

E6 High Quality SCD

E6 Standard SCD

Ho

le d

en

sity

(cm

-2)

1000/T (K-1

)

Carriers density value of 1013 cm-2 is

temperature independent, as expected

for 2D transport in extended states

and in the absence of localizations.

Mobility activation occurs around 50-60 K

When T<50 K, µ is T independent with very low EA

Mobility and carriers activation energy EA are in relation with diamond surface

quality, in particular to surface roughness and crystallographic defects

Hydrogen Termination AnalysisHall mobility



11/26

a) C.E. Nebel, F. Ertl , C. Sauerer , M. Stutzmann , C.F.O. Graeff , P. Bergonzo , O.A. Williams, R.B. Jackman Diamond Relat. Mater. 11 (2002) 351–354

b) K. Hayashi, S. Yamanaka, H. Watanabe, T. Sekiguchi, H. Okushi, K. Kajimura J. Appl. Phys. 81 (1997) 744-753

c) J. A. Garrido, T. Heimbeck, And M. Stutzmann Phys. Rev. B71 (2005) 245310

100

101

102

101

102

103

E6 HQ SCD

E6 St SCD

RAS SCD P14MS

RAS PolyD4

PolyCVD (A) Ref.[a]

Nat.IIa (C) Ref.[a]

SCD Ref.[b]

SCD Ref.[c]

Hall

Mo

bil

ity (

cm2/V

s)

1000/T (K-1

)

Higher RT values have been

found with different techniques

Hydrogen Termination AnalysisSurface doping

10-13

10-11

10-9

10-7

10-5

-6 -4 -2 0 2 4 6

H-Terminated

SCD SQ E6

4.5x4.5x0.5 mm

Al/Au 205K

207.5

220K

240K

260K

280K

292K

300K

Cu

rren

t (A

)

Voltage (V)

B=0.75 0.05 eV

Rs= 38 k

n= 1.3



12/26

diamondReactive Ion Etching (RIE)

Ar + O2 Ar + O2

Resist

H

diamond Hydrogen Termination:

H-terminated layer

Device Technology Issues

Ohmic Contact

Au

Drain-Source Channel

Wet etching: KI+O2+H20

EBL resist

Gate Electrode EBL resist

Aluminum

After EBL resist stripping



13/26

Device Layout

25 μm ≤ WG ≤ 200 μm

0.2 μm ≤ LG ≤ 1 μm

Small H-terminated area for leakage current reduction and

electric field confinement.

2D Hole Channel

Drain(Au)

Gate(Al)Source

(Au)Source

(Au)

CVD Diamond

WG




14/26

C-V and charge carriers depth profile

130

20

; sd d

s

AdN x x

qA dVC C

C

-4 -3 -2 -1 0 1 2 3 4

SAG FET

L=400 nm, W=50 m

1MHz

Cap

aci

tan

ce (

pF

) C-2 x

10

24 (F

-2)

Voltage, VGS

(V)

10

5

15

20

25

0

0.6

0.4

0.8

1

1.2

0

0.2

0.93 pF

VBi

=-0.1V


1 10 100

100 kHz

10 kHz

1 MHz

Ho

le D

en

sity

x1

01

3 (

cm

-2)

xd (nm)

10

1.0

0.1

0.01

Self-Aligned Gate FET

LG

=1 m

WG

=200 mf

Tail

Channel

Increasing frequency the channel is

pushed down below the surface

1/2

0dx x



15/26

0

5

10

15

20

-3 -2 -1 0 1 2

TM180 E6 IV21

L = 2 m W = 50 m

Vds=0.00

-0.50

-1.00

-1.50

-2.00

-2.50

-3.00

-3.50

-4.00

-4.50

-5.00

-5.50

-6.00

-6.50

-7.00

-8.00

-10.00

-13.00

-20.20

-25.00

|ID

S| (

mA

/mm

)

VGS

(V)

Vth

Thermal Management Grade E6 No-SAG

0

1

2

3

4

5

6

7

8

-3 -2 -1 0 1 2

TM180 E6 IV21

L = 2 m

W = 50 m0.00

-0.50

-1.00

-1.50

-2.00

-2.50

-3.00

-3.50

-4.00

-4.50

-5.00

-5.50

-6.00

-6.50

-7.00

-8.00

-10.00

-13.00

-20.20

-25.00

gm

(m

S/m

m)

VGS

(V)

VDS

Mobility degradation and/or

series resistance effects

Short channel effects are visible


DC and RF MESFETs performances



16/26

-20

-10

0

10

20

30

40

0,1 1 10 100

MAG [dB]

|H21

|2 [dB]

VDS

= -18 V VGS

= 0.0 V

Gain

(d

B)

Frequency (GHz)

LG= 200 nm

WG=200 µm

fMAX=14.1 GHz

fT=4.1 GHz

Thermal Management Grade TM180 by Element Six

-20 dB/dec.

Gain@1GHz

11 dB

Old RF Layout

fMAX/fT=3.5

-20

-10

0

10

20

30

40

0,1 1 10 100

MAG [dB]

|H21

|2 [dB]

VDS

= -14 V VGS

= -0.3 V

Gain

(d

B)

Frequency (GHz)

New RF Layout

LG= 200 nm

WG=50 µm

fMAX=14.9 GHz

fT=6.1 GHz

-20 dB/dec.

Gain@1GHz

15 dB

fMAX/fT=2.4

DC and RF MESFETs performances TM180 by Element Six SAG FET

Slight dependence on VDS addresses not yet saturated carrier velocity



17/26

TM180 by Element Six SAG FET

Better performance is obtained

near the threshold voltage VTh

New RF Layout

Near the threshold, CGS decreases

faster than gm,p: holes channel charge

is pushed into the substrate down to a

region of higher mobility.

0,1

1

10

-4-3-2-10123

fMax

fT

Freq

uen

cy (

GH

z)

VGS

(V)

VDS

=-14V

VGS

=-0.3V

10-13

10-12

1

10

-4-3-2-10123

Ca

pa

cita

nce

(F/m

m) g

m,p (m

S/m

m)

VGS

(V)

gm,p

CGS

gm,max

LG= 200 nm

WG=50 µm

0

5

10

15

20

25

30

35

0 2 4 6 8 10 12 14

New Layout

Old Layout

f Ma

x (G

Hz)

fT (GHz)

=3.3

=2.0




18/26

0

20

40

60

80

100

120

140

0 20 40 60 80 100

0.0 V

-0.25 V

-0.5 V

-0.75 V

-1.0 V

-1.25 V

-1.5 V

-1.75 V

-2.0 V

-2.25 V

-2.5 V

-2.75 V

-3.0 V

-3.25 V

-3.5 V

I DS (

mA

/mm

)

VDS

(V)

RAS P7MS SAG

LG

=0.4 m, WG

=25 m

VGS

RAS Single Crystal Diamond

Channel conductance is always positive. No self-heating effects!

70VFappl = 1.87 MV/cm

0

20

40

60

80

100

120

0

10

20

30

40

50

-4 -3 -2 -1 0 1

RAS P7MS SAG

LG=0.4 m

WG=25 m

-5V

-20V

-60V

gm (mA/mm/V) Vds=-5V



I DS (

mA

/mm

)

gm

(mS

/mm

)

Vgs (V)

VTh

=-0.4V

Threshold Voltage=-0.4V




19/26

-10

0

10

20

30

40

0,1 1 10 100

MAG [dB]

|H21

|2 [dB]

Ga

in (

dB

)

Frequency (GHz)

-20 dB/dec.

VGS=-0.2 V, VDS=-10 V

Gain = 15 dB@ 1 GHz

Eapplied= 0.5 MV/cm

WG=25 μm

fMAX = 23.7 GHz

fT = 6.9 GHz


RAS PolyD4

fMAX/fT=3.5-10

0

10

20

30

40

0,1 1 10 100

MAG [dB]

|H21

|2 [dB]

Ga

in (

dB

)

Frequency (GHz)

Single Crystal Diamond

RAS P7MS

Wg=50 μm

fMAX =26.3 GHz

fT = 13.2 GHz

Gain = 22 dB @ 1 GHz

fMAX/fT=1.8

LG=0.2 μm

RF PerformancesDC and RF MESFETs performances



20/26

-20

-10

0

10

20

30

40

0,1 1 10 100

MAG [dB]

|H21

|2 [dB]

Ga

in (

dB

)

Frequency (GHz)

-20 dB/dec.

Lg=0.2 μm, Wg=25 μm

VGS=0.0V, VDS=-35V

Gain =

16 dB @1GHzfMax = 35 GHz

fT = 9.3 GHz

Eapplied= 1.75 MV/cm

Cut-off frequencies increase according

to drain source applied electric field,

suggesting that charge carriers

saturation velocity is not reached yet

P. Calvani, A. Corsaro, M. Girolami, F. Sinisi, D.M. Trucchi, M.C. Rossi, G. Conte, S. Carta, E. Giovine, S. Lavanga , E. Limiti , V. Ralchenko “DC and RF

Performance of surface channel MESFETs based on hydrogen terminated polycrystalline diamond”, Diamond Relat. Mater. 18, (2009) 786-788

PolyD4 by Russian Academy of Sciences

RF PerformancesDC and RF MESFETs performances



21/26

Class A @ 1GHz

Pout=0.8 W/mm

G. Conte, et al. “RF Power Performance Evaluation of

Surface Channel Diamond MESFETs”, Solid State Electr.

55 (2011) 19-24

Best reported result on SCD: Pout @1GHz=2.1 W/mm [Lg=0.1 μm, Wg=100 μm, VGS=-1.5 V, VDS=-20 V]M. Kasu, et al.,“2 W/mm Output Power Density At 1 GHz For Diamond FETs” Electr. Lett. 41 (2005) 1249

-20

-15

-10

-5

0

5

10

15

0

5

10

15

20

25

-25 -20 -15 -10 -5 0 5 10

Pout

(dBm)

Gain (dB)

PAE %

Pin

(dBm)

Po

ut (d

Bm

), G

ain

(d

B)

PA

E %

Best reported RF result for Polycrystalline Diamond

LG=200nm

WG=50um

VDS=-14 V,

VGS=-0.3 V

fMAX = 15.2 GHz

ft = 6.2 GHzLinear Gain=8 dB (–25 to 0 dBm).

This indicates the possibility of

power amplification without

distortion in a wide input range.

Power output can be increased by

reducing impedance mismatch

between the output side of the

diamond FETs and the input side of

the tuner in the power measurement

system.




22/26

First device

Year1995 2000 2005 2010

1

10

1002009

Diam. Relat. Mater. 18

2008 - IJMOT 3

SCD 2007

Graduate Thesis

2006


PolyD 2005

Graduate Thesis

H. Kawarada et al.

Appl. Phys. Lett. 65

H. Taniuchi et al.

IEEE EDL 22

K. Ueda, M. Kasu et al.

IEEE EDL 27

A. Aleksov, E. Kohn et al.


RF

per

form

an

ces

(GH

z)

10-1

100

101

102

103

0,1 1 10

fMAX

- PolyD - Kasu et al. (IEEE El. Dev. Lett., 27 - 2006)

fMAX

- SCD - Kawarada et al. (APL, 92 - 2008)

fMax

- SCD - Aleksov et al. (Diam. Relat. Mater. 11 - 2002)

All fT

fMAX

- PolyD - S2DEL

fMAX

- SCD - S2DEL

Fre

qu

ency

(G

Hz)

1/LG

( m-1

)

fT

fMax

RF Power PerformancesGate length scaling



23/26

Poly Ra270 DiamondFast optically triggered switches

0

0,5

1

1,5

2

Vds

=Floating

-1V

-2V

-3V

-4V

-5V

-6V

-7V

-8VSig

nal

(V)

Time (ns)

0 10 20 30 40-20 -10

OpFET

=193 nm

WG

=200 m; LG

=4 m

G-D=12 m

G-S=~1 m

VGS

=-2V

0

0,5

1

1,5

2

-1.0V

-1.25V

-1.5V

-1.75V

-2.0V

0.0V

-0.5V

0.5VSig

nal

(V)

Time (ns)0-5 105 2015 25

OpFET

=193 nm

WG

=200 m; LG

=4 m

G-D=12 m

G-S=~1 m

VDD

=-8V

VGS

S G D

193 nm

Strong asymmetric design and low hydrogenation

level aimed to reduce current in the dark



24/26

-0,01

0

0,01

0,02

0,03

0,04

0,05

0,06

0,07

Vds=0

Vds=-0.5

Vds=-1.0

Vds=-1.5

Vds=-2.0

Vds=-2.5

Vds=-3.0

Vds=-3.5

Vds=-4.0

Vds=-4.5

Vds=-5.0

Vds=-6.0

Vds=-7.0

Vds=-8.0

Peak

Am

pli

tud

e (

V)

Vdd

(V)

0 -2 -4 -6 -8

Diamond UV-FET

l = 20 um

w = 200 um

ArF 193 nm

-1 -3 -5 -7

Vgs

- Vdd

100 kLeCroy

UV

RAC=1 M

Polycrystalline DiamondUV triggered MESFETs

WG=200 µm LG=4 µm

Vgs=-0.9 VG-S =4 µm, G-D=12 µm

G. Conte, G. Ricciotti, P. Calvani, E. Giovine,

Diamond FET: high-speed optical switch

Electronics Lett., 46 (2010) 1614-1616



25/26

Conclusions

MESFETs on H-terminated poly-diamond are ready for technogical transfer

to the industry (at least for High Frequency low-Power applications)

Polished substrates up to 2x2 cm2 are today available

Best reported microwave performances

Large grains substrates show better H-termination

Low roughness for scaling down the gate-contact by EBL is requested

SCD could be used to study new device architectures (i.e. -doping)

Limited dimension

Replica of crystallographic defects from HPHT substrates

Difficulty to grow i-Diamond on B-doped layers

Mathematical modeling is welcome for devices performance improvement

Fast optical switch behavior has been demonstrated

Opaque gate three-terminal devices are suitable for application in emerging

photonic technologies, for power-management systems optical receivers,

where copper wires and EM shielding can be replaced by lightweight optical

fibres



26/26

Thanks for your attention

Authors would like to acknowledge:

E. Limiti, W. Ciccognani

G. Ghione, F. Cappellutti

Surface Channel MESFETs on H-Terminated Diamondasdn.net/ngc2011/presentations/conte.pdf•1987:...

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