Folie 1 - MOS-AK
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Transcript Folie 1 - MOS-AK
Modeling Intermodulation Distortion in
HEMT and LDMOS Devices Using a New
Empirical Non-Linear Compact Model
Toufik Sadi and Frank Schwierz
Department of Solid-State Electronics,
Technische Universität Ilmenau,
D-98684 Ilmenau, Germany
[email protected]
MOS-AK/GSA Workshop Paris - 7th & 8th April 2011
Outline
Objectives
Motivation
Non-linearities in semiconductor devices
Non-linear FET models
Compact modeling of III-V HEMTs and LDMOSFETs
Motivation
New in-house model
Validation
Summary
MOS-AK/GSA Workshop Paris - 7th & 8th April 2011
Compact Modeling of III-V HEMTs
Framework: Within the COMON (COmpact MOdelling
Network) project funded by the European Union
Aim: Development of improved universal HEMT models
Objectives:
Efficient current-voltage, charge and noise models
GaAs, GaN HEMTs and other high-power devices
Focus: Non-Linearities in HEMTs
Intermodulation distortion (IMD)
Included Effects:
Self-heating; frequency dispersion; etc..
MOS-AK/GSA Workshop Paris - 7th & 8th April 2011
Motivation
Non-linear HEMT Models
Design of modern microwave circuits and systems
Minimization of Intermodulation Distortion
Current-Voltage (I-V) Model
Accurate modeling of I-V characteristics and derivatives
Inclusion of electrothermal & frequency dispersion effects
Applicable to GaAs and GaN HEMTs, and to Si LDMOS FETs
Effective parameter extraction and fitting routines
Modeling of IMD figures of merit using Volterra series analysis
Charge (C-V) Model
Correct modeling of C-V characteristics is sufficient
Using simple/existing models
MOS-AK/GSA Workshop Paris - 7th & 8th April 2011
Non-Linearities in Electron Devices
Almost everything in semiconductor electronics is nonlinear !!!
Non-linear I-V characteristics
Distortion of the output signal shape
New frequency components appear
2nd order: 2xf
3rd order: 2xf, 3xf
nth order: 2xf, 3xf,…,nxf
Linear output
V V cos(t )
15
1
GS
I (t ) K V K V
d
1
K V
3
GS
GS
3
2
K V
4
GS
GS
4
2
30
5
20
0
-5
-10
K V
5
10
Output (a.u.)
I (t ) K V
d
40
Output Signal
P
Drain current (a.u.)
GS
Non-linear output
5
-15
0.0
GS
MOS-AK/GSA Workshop Paris - 7th & 8th April 2011
10
0
-10
0.5
1.0
Time
1.5
2.0
-20
0.0
0.5
1.0
Time
1.5
2.0
Intermodulation in HEMTs
Two-tone Input
Input with two frequency components f1 and f2
Vin t V1 t V2 t A1 cos 1 t A2 cos 2 t
Example: 3rd order transfer characteristics
Vout t 0 : DC
th
st
1 : f1 , f 2
2 : 2 f1 , 2 f 2 , (f1 f 2 ), ( f1 f 2 )
nd
3 : 3 f1 , 3 f 2 , (2f1 f 2 ), (2 f1 f 2 ),
rd
(2f 2 f1 ), ( 2 f 2 f1 )
Signal (Intermodulation ) components at new
frequencies are generated
MOS-AK/GSA Workshop Paris - 7th & 8th April 2011
Compact Models for III-V FETs
Physics-based
Analysis of effect of physical parameters (gate length, mobility, etc…)
No parameter optimization
Rigorous mathematical formula
Technology-dependent
Discontinuous (using of conditional functions)
Table-based Storing parameters at several biases in a table
No parameter optimization
Technology-dependent
Discontinuities in the model elements or their derivatives
Empirical
Simple
Flexible
Continuous
Technology-independent
Good model formulation
Parameter optimization
MOS-AK/GSA Workshop Paris - 7th & 8th April 2011
Non-Linear Empirical III-V FET Models
Curtice Model (1980) Quadratic/cubic dependence of ID on VGS
First empirical time-domain simulation model
Tajima Model (1981) Exponential dependence of ID on VDS and VGS
First empirical frequency-domain simulation model
Materka Model (1985) Quadratic/hyperbolic dependence of ID on VGS
Including drain-bias dependent pinch-off potential
Statz Model (1987) Hyperbolic/cubic dependence of ID on VGS/VDS
Temperature scalability
TOM Model(s) (1990) Exponential/cubic dependence of ID on VGS/VDS
Spatial/temperature scalability
ADS EEFET/EEHEMT Model(s) (1993) Rigorous formula
Charge-based C-V model
Chalmers Model (1992) Hyperbolic dependence of ID on VGS/VDS
First to provide a good fit for transconductance and derivatives
Auriga Model (2004) Enhanced version of the Chalmers model
MOS-AK/GSA Workshop Paris - 7th & 8th April 2011
Chalmers Model for HEMTs – Advantages
Infinitely differentiable hyperbolic functions
Inherent reconstruction of the bell-shape of
Gm(VGS) for GaAs HEMTs
Reliable modeling of the higher order
derivatives of Gm(VGS) curves
Continuity – no conditional functions
Possibility of readily including several
effects, such as temperature effects,
frequency dispersion, and soft-breakdown
Simple procedure for parameter extraction
Suitability for intermodulation distortion studies
MOS-AK/GSA Workshop Paris - 7th & 8th April 2011
Angelov et al, IEEE Trans. MTT,
vol. 40, p. 2258, 1992
Chalmers Model for HEMTs – Limitations
I D I PK [1 tanh{ (VGS )}] tanh(VDS )(1 VDS )
Angelov et al,
IEEE Trans. MTT,
vol. 40, p. 2258,
1992
n
(VGS ) Pn (VGS VPK ) i
i 1
I PK Drain current at gm
max
(at VGS VPK )
P gm / I
1
max
PK
Limited suitability to model high-power devices and new structures such as
GaN HEMTs and LDMOSFETs (Fager et al., IEEE MTT, p. 2834, 2002; Cabral et al., MTTS 2004)
Saturation current (ISAT) is limited to 2IPK
Improved model to provide much more
independent control of the shape of the
current and transconductance curves while
maintaining the principal advantages of the
Chalmers model
MOS-AK/GSA Workshop Paris - 7th & 8th April 2011
New Current-Voltage Model (1)
I [ F (VGS ) F (VGS ) ] tanh(VDS )(1 VDS )
f(VGS)
f(VDS)
F (VGS ) I PK (1 tanh{ f (VGS ) }) VGS VPK 0
F (VGS ) ( I SAT I PK ) tanh{ f (VGS ) } VGS VPK 0
f (VGS ) EC ln(1 exp{g (VGS ) / EC })
f (VGS ) EC ln(1 exp{g (VGS ) / EC })
MOS-AK/GSA Workshop Paris - 7th & 8th April 2011
New Current-Voltage Model (2)
n
g (VGS ) Pn {h(VGS ) }i
i 1
g (VGS )
I PK
I SAT I PK
n
P {h(V
i 1
n
i
GS
) }.
2
2
2
2
2
2
2
2
h (VGS ) VGSN (VGSN VTN 1 ) VTN 2 VTN 1 VTN 2
h (VGS ) VGSP (VGSP VTN 1 ) VTN 2 VTN 1 VTN 2
VGSP VGSN VGS VPK
MOS-AK/GSA Workshop Paris - 7th & 8th April 2011
New Current-Voltage Model (3)
ISAT: IMAX = 2IPK
EC: more flexibility for
VTN: fine-tuning
I-V curves & derivatives
parameters
Fager et al., IEEE MTT, p. 2834, 2002
MOS-AK/GSA Workshop Paris -
7th
&
8th
April 2011
I-V Model Advantages
Continuous – closed-form expression
Accurate modeling of I-V characteristics and derivatives
GaN HEMT (Cabral et al., MTTS 2004)
LDMOS FET (Fager et al., IEEE MTT, p. 2834, 2002)
Simple parameter extraction & fitting procedure
Applicable to GaAs, GaN HEMTs; LDMOS FETs;
MOS-AK/GSA Workshop Paris - 7th & 8th April 2011
I-V Curves
Pulsed (300K)
Static DC
0.25m gate-length GaAs pHEMT [1]
VGS : -1.2V to -0.4V — Step = 0.1V
0.35m gate length GaN HEMT [2]
VGS : -4V to 0V — Step = 1V
[1] K. Koh et al, in Proc. IEEE IMS, p. 467, 2003
[2] J.-W. Lee et al, IEEE Trans. MTT, vol. 52, p. 2, 2004
MOS-AK/GSA Workshop Paris - 7th & 8th April 2011
LDMOS FET from [3]
VGS : 3 and 5V
[3] C. Fager et al, IEEE Trans. MTT, vol. 50, p. 2834, 2002
Volterra Series Analysis
Modeling the contribution of the current source to non-linearities
Two-tone excitation input – Vin Vs
cos( t ) cos( t )
1
2
Results are from the GaAs pHEMT *
Pin = -20dBm, RL = RS = 50 Ohm
*K. Koh et al, in Proc. IEEE IMS, p. 467, 2003
MOS-AK/GSA Workshop Paris - 7th & 8th April 2011
Plin, PIM2, PIM3: linear, 2nd and 3rd order power
IP2, IP3: 2nd and 3rd order interception points
Accomplished Work (5)
IMD analysis in high-power GaN HEMTs and LDMOSFETs
GaN HEMT (Cabral et al., MTTS 2004)
LDMOS FET (Fager et al., IEEE MTT, p. 2834, 2002)
MOS-AK/GSA Workshop Paris - 7th & 8th April 2011
Conclusions
New flexible empirical non-linear model
Minimized parameter fitting
Accurate calculation of higher-order derivatives
Suitable for intermodulation distortion modeling
Applicable to a wide range of devices
Acknowledgments
This work is funded by the European Union, in the
framework of the COMON project.
MOS-AK/GSA Workshop Paris - 7th & 8th April 2011