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Agilent EEsof EDA

February 26, 2008 1

Nickolas Kingsley, PhDYusuke Tajima, PhD

Auriga Measurement Systems650 Suffolk Street, Suite 410

Lowell MA, 01854 USA

Large signal model extraction of GaAs MESFETs and GaN

HEMT Devices

2

Introduction

1. Modeling steps will be described for small signal, noise, and large signal models

2. Model extraction examples will be presented for GaAs pHEMTs and GaN HEMT devices

3

Topics

1. Model extraction programs2. Small signal and noise model

extraction3. Large signal model extraction steps

4

Model extraction programs

1. ICCAP(Agilent)Versatile extraction platform.Customer can add extraction process for different models.

2. Model Station (Auriga)Limited to FET family of devices.Good for small signal, noise and large signal models.Generates models compatible for ADS and MWO.

5

Model Station Dialog Box

6

Data Inputs to Model Station

Small signal data inputs

Large signal data inputs

7

Topics

1. Model extraction programs2. Small signal and noise model

extraction3. Large signal model extraction steps

CAPID=CdsC=0.3498 pF

CAPID=CgdC=0.1065 pF

CAPID=CgsC=1.906 pF

INDID=LdL=0.118 nH

INDID=LgL=0.1378 nH

INDID=LsL=0.001114 nH

RESID=RiR=0.5284 Ohm

1

2

3

4

VCCSID=U1M=0.1935 SA=0 DegR1=1817 OhmR2=88.48 OhmF=0 GHzT=2.5 ps

INDID=LgdL=0 nH

RESID=RgdR=0 Ohm

T1 2

RESTID=Rd1R=1.029 OhmT=16.85 DegC

T1 2

RESTID=Rg1R=2.536 OhmT=16.85 DegC

T

1

2

RESTID=Rs1R=0.4443 OhmT=16.85 DegC

CAPID=CggC=0 pF

RESID=RggR=1e5 Ohm

PORTP=1Z=50 Ohm

PORTP=2Z=50 OhmID=EN1 ID=EN2

ID=EN3

ID=EN4

ID=EN5

ID=EN6 ID=EN7ID=EN8 ID=EN9

ID=EN10

ID=EN11

ID=EN12

ID=EN13Cval=.5

8

Small signal model

9

150x80 1.

01

.0-

1.0

10.

0

10.0

-10.0

5.0

5.0

-5.0

2.0

2.0

-2.0

3.0

3.0

-3.0

4.0

4.0

-4.0

0.2

0.2

-0.2

0.4

0.4

-0.4

0.6

0.6

-0.

6

0.8

0.8

-0.

8

S11 and S22Swp Max26.4GHz

Swp Min0.2GHz

S(1,1)FET Schematic

S(1,1)SParm Data

S(2,2)FET Schematic

S(2,2)SParm Data

0

15

30

45

60

75

90

105

120

135

150

165

-180

-165

-150

-135

-120

-105 -9

0

-75

-60

-45

-30

-15

S12Swp Max

26.4 GHz

Swp Min0.2 GHz

Mag Max0.05

0.01Per Div

S(1,2)FET Schematic

S(1,2)SParm Data

0

15

30

45

60

75

90

105

120

135

150

165

-180

-165

-150

-135

-120

-105 -9

0

-75

-60

-45

-30

-15

S21Swp Max

26.4 GHz

Swp Min0.2 GHz

Mag Max20

5Per Div

S(2,1)FET Schematic

S(2,1)SParm Data

10

Extraction of Models at multiple bias points

11

Small signal model with noise sources

CAPID=CdsC=0.03942 9 pF

CAPID=CgdC=0.02953 pF

CAPID=CgsC=0.125579 pF

INDID=LdL=0.007666 nH

INDID=LgL=0.000293 nH

INDID=LsL=0.001929 nH

RESID=RiR=0.5 Ohm

T1 2

RESTID=RgR=2.07231 OhmT=16.85 DegC

T

1

2

RESTID=RsR=1.98319 OhmT=16.85 DegC

1

2

3

4

VCCSID=U1M=0.09605 SA=0 DegR1=979421 OhmR2=190.957 OhmF=1e18 GHzT=0.391458 ps

1

2

3

4

VINCORID=VIN1V1SQ=0.020672I2SQ=1043.23CorrR=0.123144CorrI=0.303625

T1 2

RESTID=RdR=2.60038 OhmT=16.85 DegC

INDID=LgdL=0 nH

RESID=RgdR=0 Ohm

CAPID=Cgg1C=0 pF

RESID=Rgg1R=100000 Ohm

PORTP=1Z=50 Ohm

PORTP=2Z=50 Ohm

Noise is generated from parasitic resistive elements as well as intrinsic noise sources as shown here. Noise sources are defined by voltage and current noise sources and correlation (complex) between them.

12

Noise parameters simulated from extracted model are compared with the measured results (Vd=0.9V, 8mA)

Freq 2-26GHz

13

Topics

1. Model extraction programs2. Small signal and noise model

extraction3. Large signal model extraction steps

14

Large signal model extraction steps

1. Extraction of Auriga model- Charge conservation satisfied

2. Our modeling steps- Define de-embedding parameters.- DC IV- Pulsed IV- (Pulsed) S parameters- Temperature test- Loadpull verification

15

Many models draw non-physical gate current because they were violating Charge Conservation Law

Cgs(Vgs, Vds)

Vgs Vds

0

0.1

0.2

0.3

0.4

0.5

0.6

-1.5 -1 -0.5 0 0.5 1

Cgs(pF) vs Vgs with Vds as a parameter

Vd=0V

Vd=0.5V

Vd=1VVd=2V

Vd=3VVd=4V

Vd=5V

Vd=6V

Typical Cgs dependency on gate and drain voltages

16

Charge conservationAs is well known, if the charge conservation is not

satisfied at terminals, the device model will draw non-physical current in order to maintain charge neutrality under RF drive.

VgsVgdVgsCgd

VgdVdsVgsCgs

∂∂

=∂

∂ ),(),(

Capacitors are constrained by the equation above in new Auriga model (LS6)

17

0 10 20 30 32Power (dBm)

Gate Current 50ohms A

0

0.01

0.02

0.03

0.04A

0

0.01

0.02

0.03

0.04

A

p2

|Icomp(I_METER.AMP2,0)|[*,X] (L)50ohm power simulation LS6

|Icomp(I_METER.AMP1,0)|[*,X] (R, A)50ohm power simulation LS6

|Icomp(I_METER.AMP1,0)|[1,X] (R, A)50ohm power simulation LS5

|Icomp(I_METER.AMP2,0)|[*,X] (L)50ohm power simulation LS5

p1: Freq = 2.6 GHz

p2: Freq = 2.6 GHz

Traditional(LS5)

Data

Gate current under RF driveMeasured data vs traditional model (LS5)

Without charge conservation, a large non-physical current flows through gate terminal. This is not real.

18

Charge Conserved Model (LS6)vs Traditional model (LS5)

(Example: Gate current behavior under RF drive.)0 10 20 30 32

Power (dBm)

Gate Current 50ohms A

0

0.01

0.02

0.03

0.04A

0

0.01

0.02

0.03

0.04

A

p2

|Icomp(I_METER.AMP2,0)|[*,X] (L)50ohm power simulation LS6

|Icomp(I_METER.AMP1,0)|[*,X] (R, A)50ohm power simulation LS6

|Icomp(I_METER.AMP1,0)|[1,X] (R, A)50ohm power simulation LS5

|Icomp(I_METER.AMP2,0)|[*,X] (L)50ohm power simulation LS5

p1: Freq = 2.6 GHz

p2: Freq = 2.6 GHz

Traditional(LS5)

Charge conserved (LS6)

Data

With charge conserved model, gate current under rf drive is well simulated.

19

Large signal model extraction steps1. Extraction of Auriga model

- Charge conservation satisfied

2. Our modeling steps- Define de-embedding parameters.- DC IV- Pulsed IV- (Pulsed) S parameters- Temperature test- Small signal and Loadpull verification

20

De-embedding

235um 235um

A A’B B’

Reference planesMeasurement A-A’Modeling B-B’

1

2

3

Auriga_LS6_FETID=MF1DESC=8x100AFAC=1AL=1Temp=23.85 DegC

MLINID=TL1W=0.076 mmL=0.3 mm

MLINID=TL2W=0.076 mmL=0.3 mm

PORTP=1Z=50 Ohm

PORTP=2Z=50 Ohm

AA’B

B’

Input de-embedding box

Output de-embedding box

21

Our modeling steps

- Define deembedding parameters.- DC IV- Pulsed IV- (Pulsed) S parameters- Temperature test- Small signal and Loadpull verification

22

DC IV measurement

1. This is an important step to screen chips and select the chips for modeling.

2. DC is used to measure gate diode characteristic for both forward and reverse.

23

Measurement of Diodes between G-S and G-D

VdIg

VgG

D

S

VdIg

VgG

D

S

D1

D2

0.0V

0.5V

1.0, 1.5, 2.0V

VdCurrent limit

D2D1+D2

24

Our modeling steps

- Define deembedding parameters.- DC IV- Pulsed IV- (Pulsed) S parameters- Temperature test- Small signal and Loadpull verification

25

Pulsed IV and S parameter measurements

Characterization using pulse technique becomes only tool to measure large devices within thermal limits.

- Pulsed IV- Pulsed S parameters

26

Principle of Pulsed IV

All the IV data are measured in short pulses while the bias point is kept at the quiescent point .

0

1000

2000

3000

4000

5000

6000

0 10 20 30 40 50 60 70 80 90 100

Id (m

A)

pe

ak 5

.3 a

mps

Vd (volts)

QuiescentVd = 50 vId = 150 mA

Vg 2.0

Vg 1.0

Vg 0

Vg -0.5

Vg -1.0

27

Pulsed IV system AU4550

AU4550

Pulser

Pulser

DUT

28

Why Pulsed IV?1. Thermal 2 Field induced traps

Quiescent condition 0Vd, 0Vg Quiescent condition 6Vd,-4Vg

Pulsed IV data of a pHEMT at different quiescent conditions

29

Pulsed IV and IV Model

(Blue) Pulsed IV Data Quiescent point (50V, 200mA)(Red) Modeled Pulsed IV

0 20 40 60 80 100Vds (Volts)

IV Curves

0

1

2

3

4

5

6

Id(A

)

30

Different results for Cgd and Rds between CW(10Vds) and Pulsed bias (10Vds peak, 50V quiescent)

Strong quiescent bias dependency on Cdg and Rds!

CW and Pulsed Cgd

0

1

2

3

4

5

-2 -1.5 -1 -0.5 0

Vgs (V)

Cgd

(pF)

Pulsed

CW

CW and Pulsed Rds

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

-2 -1.5 -1 -0.5 0Vgs (V)

Rds

(Ohm

)

Pulsed

CW

31

Similar Results for Cgs and Gm Between CW(10V) and Pulsed Bias (10Vds Peak, 50V Quiescent)

CW and Pulsed gm 10Vds

0

0.5

1

1.5

2

2.5

-2 -1.5 -1 -0.5 0

Vgs(V)G

m (S

)

Pulsed

CW

CW and Pulsed Cgs

0

10

20

30

40

50

-2 -1.5 -1 -0.5 0

Vgs (V)

Cgs

(pF)

CW

Pulsed

Cgs, Gm showed little dependency on quiescent bias condition

32

Pulsed S Parameter Set up

Bias Tee

Bias Tee

PNA

Bias Tee

Bias Tee

VNA

DUT

VNA was used to take S parameters during the pulsed bias applied through bias tees.

33

S parameter data

1. S parameters are taken over 50-150 bias points to derive small signal equivalent circuit model as a function of terminal voltages.

2. Voltage dependent Cgs, Cds and Cgd are modeled and parameterized into the Auriga large signal model.

34

Our modeling steps

- Define deembedding parameters.- DC IV- Pulsed IV- (Pulsed) S parameters- Temperature effect- Small signal and Loadpull verification

35

How short the pulses need be to be isothermal?

50 nSec sliding data window

Vds

Ids

Vq

Iq

t =0 t=tmaxT1 T2

dwell time2Vg

1Vg

0Vg

-1Vg

Id mA

IV Curves were measured between 0.2 and 50µsec on a GaN HEMT. No noticeable difference was observed. It can be concluded that channel temperature stays the same in this time frame for this device.

36

Temperature dependent IV curve model

-0.0344 50 100Vds (Volts)

IV Curves

-0.5

0

0.5

1

1.5

Id(A

)

25C

-0.0362 50 100Vds (Volts)

IV Curves

-0.5

0

0.5

1

1.5

Id(A

)

Model was derived from 25C pulsed IV data. Then scaled to other temperatures (0, 80, 150C) and compared to the pulsed IV data.

Blue: Pulsed IV DataRed: ModelVd=0-100VVdq=50V

0C

37

Temperature dependent IV curve model (2)

-0.0254 50 100Vds (Volts)

IV Curves

-0.5

0

0.5

1

1.5

Id(A

)

-0.0348 50 100Vds (Volts)

IV Curves

-0.2

0

0.2

0.4

0.6

0.8

1

Id(A

)

80C

Blue: Pulsed IV DataRed: ModelVd=0-100V

150C

38

Temperature model

))(*1(*)())(*1(*)())(*1(*)(

TnomTempTcoefRRdTRdTnomTempTcoefRRsTRsTnomTempTcoefIdsTIds

−+=−+=−+=

Temperature and Size scaling factors are available on the schematic.

39

Model Scaling

Scalable parameters-Intrinsic device parameters including currents, capacitors and resistive components (Ids, Cgs, Cgd, Rg, Rs, Rd)

Non Scalable parameters- Inductive components (Ld, Lg, Ls) - External circuit

Scalable models save time and

money

40

Our modeling steps

- Define deembedding parameters.- DC IV- Pulsed IV- (Pulsed) S parameters- Temperature effect- Small signal and Loadpull verification

41

Large signal model (Auriga LS6) Small signal verification (0.4-12GHz)

0 1.0

1.0

-1.

0

10.

0

10.0

-10.0

5.0

5.0

-5.0

2.0

2.0

-2.0

3.0

3.0

-3.0

4.0

4.0

-4.0

0.2

0.2

-0.2

0.4

0.4

-0.4

0.6

0.6

-0.

6

0.8

0.8

-0.

8

S11 and S22Swp Max

11.99GHz

Swp Min0.38GHz

S(1,1)FET Schematic

S(1,1)SParm Data

S(2,2)FET Schematic

S(2,2)SParm Data

0

15

30

45

60

75

90

105

120

135

150

165

-180

-165

-150

-135

-120

-105 -9

0

-75

-60

-45

-30

-15

S21Swp Max

11.99 GHz

Swp Min0.38 GHz

Mag Max20

5Per Div

S(2,1)FET Schematic

S(2,1)SParm Data

0

15

30

45

60

75

90

105

120

135

150

165

-180

-165

-150

-135

-120

-105 -9

0

-75

-60

-45

-30

-15

S12Swp Max

11.99 GHz

Swp Min0.38 GHz

Mag Max0.06

0.02Per Div

S(1,2)FET Schematic

S(1,2)SParm Data

S11, S22 S21 S12

40Vd –1.0Vg

S parameter simulation from the large signal model was verified over a wide bias range.

42

Load Pull Testing and Simulation Results

DUTFixtured device

Focus iTuner708

ElectronicTuner

Load pull system

PA

Source

ReceiverBias Tee

Bias Tee

Power Supply

Power Supply

43

Loadpull simulation circuit

Prematch Fixture

Prematch Fixture3:Bias

12

HBTUNER2ID=TU1Mag1=0.58Ang1=-168 DegMag2=0.56Ang2=69.4 DegMag3=0Ang3=180 DegFo=2 GHzZo=50 Ohm

0 mA

SU

0 mA

3:Bias

1 2

HBTUNER2ID=TU2Mag1=0.56Ang1=84.9 DegMag2=0.4Ang2=-63.1 DegMag3=0Ang3=180 DegFo=2 GHzZo=50 Ohm

149 mA149 mAPOP=Z=

Device Model

Pin Pout

44

Device Simulation vs Single Tone Load Pull Data @ 2GHz

0 10 20 30 34Power (dBm)

Load pull adjusted source and load termination

10

20

30

40

50

0

20

40

60

80

p2

p1AMtoAM(PORT_2)[1,X,*] (L, dBm)Adjusted Load PullPAE(PORT_1,PORT_2)[1,X,*] (R)Adjusted Load Pull|Icomp(DCVS.V3,0)|[1,X,*] (R)Adjusted Load Pull|Icomp(DCVS.V4,0)|[1,X,*] (L)Adjusted Load Pull

PlotCol(1,2) (L)30LF run 1 w AMPMPlotCol(1,4) (R)30LF run 1 w AMPMPlotCol(1,6) (R)30LF run 1 w AMPM

p1: Freq = 2 GHzVg = -1.08

p2: Freq = 2 GHzVg = -1.08

%dBm Max Power47dBm

Max Eff67%

45

Device Simulation vs Two Tone Load Pull Data @ 2GHz

IM3

IM5

SimulationdBm

46

Summary

Modeling extraction steps for small signal and large signal model are described in this presentation using GaAs pHEMTs and GaNHEMT device data.Difficulties of modeling large devices, such as GaN HEMTs with 100W output power, were discussed.These models were used successfully to simulate 2.1GHz 100W GaN HEMT amplifier.

Thank you

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