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ASM-HEMT: Compact Modeling of GaN HEMTs for High Frequency and
High Power ApplicationsDr. Yogesh S. Chauhan
Associate ProfessorNanolab, Department of Electrical Engineering
IIT KanpurEmail: [email protected]
Homepage – http://home.iitk.ac.in/~chauhan/
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Outline
• Overview of Compact Modeling
• GaN HEMT
• ASM-HEMT Model Overview
• Model Validation
Yogesh S. Chauhan, IIT Kanpur 211/08/2017
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Joint Development & Collaboration
Yogesh S. Chauhan, IIT Kanpur 311/08/2017
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PDK and Compact Model
Yogesh S. Chauhan, IIT Kanpur 411/08/2017
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Enablers of a silicon chip design
Yogesh S. Chauhan, IIT Kanpur 5Source: David HARAME at. al., IBM J. RES. & DEV. MARCH/MAY 2003
11/08/2017
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Goal of a PDK – The output of Enablement
• Offer a circuit design environment that enables full exploitation of technology
• Capture all device physics• Model impact of layout choices on device mean and variance• Include typical layout effects for simulation from schematic• Accurate modeling of layout effects for simulation from layout
Yogesh S. Chauhan, IIT Kanpur 6
Enablement PDKKey to Happy Designers!!Technology Innovation Circuit Designers
11/08/2017
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Compact Modeling or SPICE Modeling
• Excellent Convergence• Simulation Time – ~µsec• Accuracy requirements
• ~ 1% RMS error after fitting• Example: BSIM6, BSIM-
CMG
Medium of information exchange
Good model should be Accurate: Trustworthy simulations. Simple: Parameter extraction iseasy.
Balance between accuracy andsimplicity depends on end application
Yogesh S. Chauhan, IIT Kanpur 711/08/2017
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Industry Standard Compact Models
• Standardization Body – Compact Model Coalition
• CMC Members – EDA Vendors, Foundries, IDMs, Fabless, Research Institutions/Consortia
• CMC is by the industry and for the industry
Yogesh S. Chauhan, IIT Kanpur 811/08/2017
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GaN Properties
11/08/2017 Yogesh S. Chauhan, IIT Kanpur 9[U. K. Mishra et al., Proc. IEEE, 96 (2), 287 (2008)]
Device characteristics:• High Breakdown Voltage ( )• Low ON Resistance ( )
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GaN HEMT: Advantages
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Alex Q. Huang pp. 528-531, IEDM 2016
advantage of fast gate driving capability
Reduction in switching loss in hard or soft switched converter
Reverse recovery loss reduction
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Polarization
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Wurtzite
Polarization!
[O. Ambacher et al., JAP, 85 (6), 3222 (1999)]
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GaN Wafers
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• Sapphire (Al2O3) Semi-insulating High growth temperatures Relatively cheap
• Silicon (Si) Low cost Large diametersAcceptable thermal conductivity Processing in standard silicon fabs
Low thermal conductivity Lattice mismatch CTE mismatch
Lattice mismatch CTE mismatch
• Silicon Carbide (SiC) High thermal conductivity Low Lattice mismatch Low CTE mismatch
Highly costly Smaller Wafers
[U. K. Mishra et al., Proc. IEEE, 96 (2), 287-305 (2008)] [S. L. Selvaraj et al., Proc. DRC, 53 (2012)]
Dislocations ~ 10
TEM Image of GaN on Sapphire
[S. Huang, JJAP, 47 (10), 7998 (2008)]
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GaN HEMT Structure
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GaN
AlGaNS DG
Substrate
Graded AlGaN to GaN
AlGaN Spacer Layer (UID)
GTi/Al/Ti/AuPt/AuTi/Al/Ti/Au
2DEG
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AlGaN/GaN Hetero-structure
• The AlGaN/GaN hetero-structure is used to take advantage of the two dimensional electron gas (2-DEG)
• AlGaN/GaN materials create piezoelectric and spontaneous polarization effects using an un-doped hetero-interface
Yogesh S. Chauhan, IIT Kanpur 1411/08/2017
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2DEG Source
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1
[J. P. Ibbetson et al., APL, 77 (2), 250 (2000)]
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Design Rules – Materials Perspective
• Thickness of the barrier – 2DEG control
• Al Mole Fraction – 2DEG Concentration
• Nucleation and Buffer Layer – Dislocations
• Substrate – Thermal Properties
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GaN HEMTSome interesting features of III-nitride system: • Wide bandgap• High 2-DEG charge density• High electron mobility • High breakdown voltage • Excellent thermal conductivity• High power density per mm of gate
periphery
• GaN based HEMTs are able to operate in high frequency, high power as well as high temperature device applications
Yogesh S. Chauhan, IIT Kanpur 1711/08/2017
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Field Plates
11/08/2017 Yogesh S. Chauhan, IIT Kanpur 18[W. Saito et al., IEEE TED, 50 (12), 2528 (2003)]
and
Field Plated Structure
Distribution of
[H Huang, et al., IEEE TPEL, 29 (5), 2164 (2014)]
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Switching applications
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[X. Huang, et al., IEEE TPEL, 29 (5), 2453 (2014)]
• Small terminal capacitances• Less reverse recovery charge• Power loss is low
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Modeling GaN!
11/08/2017 Yogesh S. Chauhan, IIT Kanpur 20[L. Dunleavy et al., Microwave Magazine 11 (6), 82 (2010)]
Modeling Strategy
Existing Models
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Modeling Continued…
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Angelov model
[I. Angelov et al., IEEE T-MTT, 40 (12), 2258 (1992)] [I. Angelov et al., IEEE T-MTT, 44 (10), 1664 (1996)]
Angelov Model Deficiencies
• Emperical model with ~90 parameters
• Fails to capture non-linear behaviour and harmonic accuracy in power circuits
• Challenging to use for multiple device dimensions
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Status of Compact Model – GaN HEMT
Yogesh S. Chauhan, IIT Kanpur 22
Compact ModelGaN-HEMT
Table-Based Physics BasedEmpirical
Threshold-Voltage Based
Surface-Potential Based
Advanced SPICE Model for GaN HEMT device
CMC candidate models for industry standardization(Two models are in final phase)
•ASM-HEMT model: Our model•MIT Unified VS GaNFET (MVSG) model: MIT, Prof. D. Antoniadis
11/08/2017
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Advantages of SP-Based Model
• Better Model Scalability• Device Insight• Better Statistical Behavior• Accurate Charges and Capacitances• Better Temperature Scalability• Less number of parameters• Easier parameter extraction• Uses a single expression for all regions• Inherent Model Symmetry
Yogesh S. Chauhan, IIT Kanpur 2311/08/2017
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ASM-HEMT Model Overview
24
Analytical Solution of Schrӧdiger’s & Poisson’s
SP-Based Id Ig & ChargeModelReal Device effects included
Noise Model, Trapping EffectsModel, Self-Heating
2-DEG ChargeFermi-level (Ef),Surface-potential (SP)
Accurate I-V and C-VPhysical parametersDIBL, Rs, VS, ...
DC, AC, TransientHarmonic Simulations,Noise etc.
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ASM-HEMT Model Overview
Core Model
Yogesh S. Chauhan, IIT Kanpur 25
Analytical Solution of Schrӧdiger’s & Poisson’s
2-DEG ChargeFermi-level (Ef),Surface-potential (SP)
SP-Based Id, Ig & Charge Model
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Surface-Potential CalculationAssumptions:• Quasi-constant electric field in the potential well (triangular well
approximation)• Only the contribution of the first two sub-bands are important
Yogesh S. Chauhan, IIT Kanpur 26
• Basic device equations are transcendental in nature• We divide variation of Ef with Vg into regions to develop fully analytical expression• Regional models are combined in one analytical expression• No fitting parameters introduced, accuracy (order of nano-Volts)
Quasi-Fermi-potential and SP
S. Khandelwal, TED, VOL. 59, NO. 10, OCTOBER 201211/08/2017
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ASM-HEMT Model Overview
Yogesh S. Chauhan, IIT Kanpur 27
Core Drain CurrentModel
CLM MobilityDegradation
TemperatureDependence
Bias DependentSeries Resistance
Self-Heating
DIBLVelocity Saturation Sub-threshold Slope
Complete DrainCurrent Model
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Drain-Current Model and Intrinsic Charges
• We apply the drift-diffusion framework for carrier transport• An analytical and continuous expression for the core drain-current is
developed including the velocity-field relation and mobility degradation• Core Drain Current Model:
• Velocity-Field relation and mobility-degradation:
Yogesh S. Chauhan, IIT Kanpur 28
2sdm sdds Lvsateffsat
is the CLM parameter
• Ward-Dutton Partitioning for S/D charges• Capacitances are calculated as derivatives of the terminal charges: Cij=-dQi/dVj (i≠j), Cii=dQi/dVi (i=j)
Charge conservation
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Temperature Dependence
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Model Parameter Extraction
Yogesh S. Chauhan, IIT Kanpur 30
Set L, W, NF, TbarDevice Dimensions
Obtain VOFF, NF, CDSCD,ETA from log-IDVG, LINEAR
And Saturation
Obtain U0, UA, UB and RDS from IDVG-LIN
Obtain VSAT, Improve ETAFrom LINEAR IDVG
Obtain LAMBDA, ImproveVSAT, ETA from IDVD
Temperature Parameters
Capacitance Modeling
Model Implemented in Verilog-ASimulations performed in: ADS, Spectre, HSPICE
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List of Main Parameters
Yogesh S. Chauhan, IIT Kanpur 31
• Physical Constants• Simulation Conditions• Device dimensions• Physically-Linked
Parameters
Parameters Physical Meaning
U0 Low field Mobility
UA Mobility degradation parameter
UB Mobility degradation parameter
VOFF Cut-off Voltage of Device
VSAT Saturation Velocity
RTH Thermal Resistance
DIBL DIBL effect parameter
LAMBDA Channel length modulation
VOFFT Temperature dependence of Voff
UTE Mobility dependence of mu0
RS Source Side Resistance
RD Drain Side Resistance
….. …..
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Importance of Rd/s Model• Aggressive lateral scaling of source-drain access regions improve
the RF performance of GaN HEMT but at the cost of breakdownvoltage (BV)
• Too short Lgd increases electric field which is responsible for loweringof BV
• Scaling of Lgd also affects the fmax due to increasing Cgd and gds ofdevice
• As a trade-off, a short Lgs and optimized Lgd is required to achievehigh fT , fmax and BV altogether
• In GaN HEMT, gate-to-drain/source access region works asnonlinear resistance (Rd/s) which limits maximum drain current
• Accurate model of Rd/s is of great importance to predict the Id andgm for high power as well as high frequency GaN HEMTs
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Nonlinear source/drain access region resistance model
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Fig. 1: Nonlinear variation of source/ drain access resistances with Ids extracted from TCAD simulation and comparison with model.
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Rd/s Model Validation with Measurement
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Fig. 2: Id ‐ Vg and trans‐conductance for the Toshiba power HEMT. Different slopes above Voff in gm‐Vg: self‐heating governs the first slope while velocity saturation in access region affects second slope.
Fig. 3: (a) Ids‐Vds, (b) gds and (c) reverse Ids‐Vds fitting with experimental data. The non‐linear Rs/d model shows correct behavior for the higher Vg curves in the Id ‐ Vd plot; the S‐P based model can accurately capture the reverse output characteristics.
Effect of high access region resistance at high Vg
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Modeling of Temperature dependence
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The temperature dependence of Rd/s model is extremely important as it increases significantly with increasing temperature
Temperature dependence of 2-DEG charge density in the drain or source side access region:
Temperature dependence of Saturation Velocity:
Temperature dependence of electron Mobility:
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Temperature Model Validation
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Temperature Model Validation
Yogesh S. Chauhan, IIT Kanpur 37
Id‐Vg at three different temperatures 300, 365 and 425 K
VOFF variation
Mobility variation
VSAT variation
RDS variation
11/08/2017
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Temperature Model Validation
• Id-Vd at two different temperatures 300 and 573K
Yogesh S. Chauhan, IIT Kanpur 38
RDS Temperature dependences
VSAT variation
Mobility variation
VOFF variation
11/08/2017
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Model Validation – IEMN France data
Yogesh S. Chauhan, IIT Kanpur 39
Lg = 0.125 µm, W=100 µm
Lg = 0.35 μm
11/08/2017
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Modeling of Field-Plates in HEMTs
11/08/2017 Yogesh S. Chauhan, IIT Kanpur 40
Affects capacitance and breakdown behavior.
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Field-Plate Capacitance Modeling
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Cross‐Coupling Capacitance
Appearance of fringing electric field between the vertical wall of the GFP and the 2-DEGSFP causes the cross-coupling effect giving rise to the second plateau
Significant number of fringing field lines reach the GFP through the insulator stack in the absence of SFP causing more fringing capacitance
In the presence of the SFP, most of them end up at the SFP leading to a reduced fringing capacitance component in Cgd
Only GFP
Both FPs
Both FPs
11/08/2017 Yogesh S. Chauhan, IIT Kanpur 42
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Substrate Capacitance
(a) Field lines originating from the 2-DEG reach the substrate electrode leading to the existence of CSUBD
(b) whereas without substrate node, field lines from the drain side of the 2-DEG terminate at the 2-DEG on the source side through the GaN buffer
Vgs = −7 V Vds = 20 V
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Current Collapse
Stephen Sque - ESSDERC tutorial Sept. 2013 11/08/2017 Yogesh S. Chauhan, IIT Kanpur 44
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Current Collapse
[S. DasGupta et al., Appl. Phys. Lett. 101 (24), 243506 (2012)] Stephen Sque - ESSDERC tutorial Sept. 2013 11/08/2017 Yogesh S. Chauhan, IIT Kanpur 45
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Issues-Virtual-gate effect
[R. Vetury et al., Trans. Elec. Dev. 48 (3), 560 (2001)][T. Mizutani et al., TED 50, 2015 (2003)]
Stephen Sque - ESSDERC tutorial Sept. 2013 11/08/2017 Yogesh S. Chauhan, IIT Kanpur 46
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Issues-Buffer trapping
[E. Kohn et al., Trans. Microw. Theory Tech. 51 (2), 634 (2003)] Stephen Sque - ESSDERC tutorial Sept. 2013 11/08/2017 Yogesh S. Chauhan, IIT Kanpur 47
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Pulsed IV Measurements
0, 0
‐8, 0‐8, 0
‐8, 20
Vgq, Vdq Vgq, Vdq
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Trap Model and Pulsed IV Scheme
11/08/2017 Yogesh S. Chauhan, IIT Kanpur 49
The trapping effects are modeled with the help of two R-C sub-circuits. The generated trap voltagesVtrap1 and Vtrap2 are fed back into the model which update parameters like the cut-off voltage, sub-threshold slope, source and drain-resistances to capture the effects of traps.
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Modeling of Trapping effect
11/08/2017 Yogesh S. Chauhan, IIT Kanpur 50
Traps in GaN HEMTs play huge role in determining the performance of the device,especially in high frequency operations
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Switching Collapse Setup
Signal generator at gate terminal switches device from high negative stress voltage (Vgsq) to some value higher than Voff . Variable resistor is used to make device working in linear region of operation.
Waveform (i) is the input at the gate, which is switching the device from ON to OFF-state and vice versa. Waveform (ii) is the constant input applied at drain terminal via a variable resistor.
Waveform (iii) is showing the output drain current with time. The drain current is kept fixed at 0.3A with the help of variable resistor.
Waveform (iv) is the value of Vds which is equal to VDD when device is in OFF-state and becomes Von when device is in ON-state.
Waveform (iv) illustrates the fact that, as the device is turning ON, capacitor assumed for the trap-states start to discharge and due to reduction in depletion of 2-DEG, Von of the device recovers with time.11/08/2017 Yogesh S. Chauhan, IIT Kanpur 51
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Switching Collapse Model
Modeling of trapping effect by using RC network with different time constant. This RC network is contributing to drain-access region resistance as Rtrap (as a function of Vtrap) to capture the trapping effect on device ON-resistance (Ron)
Model-Hardware correlation for pulsed I-V, Von data for 1, 5 and 10 kHz input applied at gate terminal for various Vds. Von is the value of Vds at which the value of drain current is 0.3A. As VDD is increasing, Ron of the device increases which results in switching collapse. Measured data is from Toshiba for CMC standardization.
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Toshiba DC I-V Results for High Power HEMT
53Yogesh S. Chauhan, IIT Kanpur11/08/2017
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Room Temperature I‐V I
d (A
) (m
/s) [
E+
0]
/
Gds
' (A
/V2)
(m
/s) [
LOG
]
/
Yogesh S. Chauhan, IIT Kanpur 5411/08/2017
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Reverse IdVd @ room temperature
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Room Temperature I‐VId (A
)
g m(m
A/V)
g m’ (mA/V2)
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Log (Id) ‐ Vds (Vd>0) T=25 Log (Id) ‐ Vds (Vd<0) T=25
Id (A
)
Log (Id) ‐ Vgs T=25
Yogesh S. Chauhan, IIT Kanpur 5711/08/2017
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I‐V @ ‐20 deg CId (A
)
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Rev IdVd @ T=150 CVg from ‐12 to 3 V @ 0.5V step
Lin‐Scale
id
(m/s
) [LO
G]
/
Log‐Scale
Yogesh S. Chauhan, IIT Kanpur 5911/08/2017
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Rev IdVd @ T=‐20 CVg from ‐12 to 3 V @ 0.5V step
gds
' (m
/s) [
E-3
]
/
Lin‐Scale Log‐Scale
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I‐V @ ‐20 deg CId (m
A)
//
gm
gm’
Yogesh S. Chauhan, IIT Kanpur 6111/08/2017
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I‐V @ ‐20 deg C
Id (A
)
Log ‐Scale
Yogesh S. Chauhan, IIT Kanpur 6211/08/2017
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I‐V @ 100 deg CId (m
A)
Id (m
A)Id (m
A)
Yogesh S. Chauhan, IIT Kanpur 6311/08/2017
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Id (m
A)
Vd = 0.1, 0.5, 1 and 10V
Temperature Scaling
Yogesh S. Chauhan, IIT Kanpur 6411/08/2017
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DC I-V Results of MultifingerRF HEMT
65Yogesh S. Chauhan, IIT Kanpur11/08/2017
Lg = 125 nm, Wg = 10 × 90 μm, Lsg = 200 nm, Ldg = 1.7 μm
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DC Parameter Extraction Flow
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S. A. Ahsan, S. Ghosh, S. Khandelwal, and Y. S. Chauhan, "Physics‐based Multi‐bias RF Large‐Signal GaN HEMT Modeling and Parameter Extraction Flow", IEEE Journal of the Electron Devices Society, Sept. 2017.
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S-Parameters• Easy for high frequencies (hard to do
open/short for Z/Y)• Calculate other quantities• Cascadable• Transformation• Compatibility with simulation tools
RF Measurements
[Advanced Design System, Design Guide]
VNA Architecture
12
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De-embedding is a mathematical process that removes theeffects of unwanted embedded portions of the structurein the measured data by subtracting their contribution.
“Real” DUT SP= Measured SP–Fixture Characteristic
De-embedding : Negating effects of unwanted portion
De-embedding
[De-embedding Techniques in Advanced Design System, Agilent Manual]
13
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Device Layout and Manifolds
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Equivalent Circuit Model at RF
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Small Signal Modeling
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CgsCgd
gm gds
S. A. Ahsan, ..,Y. S. Chauhan, IEEE Journal of the Electron Devices Society, Sept. 2017.
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Impact of Gate Resistance• Large resistors Rgs and Rgd – Capture the differential gate
resistance for current flowing through the gate-source and gate-drain Schottky diodes.
• Their inclusion significantly impacts the overall gate resistance (Rg) at low frequencies as shown in Fig.
• Rsub and Csub – Capture the substrate loss at the output port.
11/08/2017 Yogesh S. Chauhan, IIT Kanpur 73
Total Rg
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S-Parameters
• Frequency: 0.5 − 50 GHz
• 2 different drain-bias conditions, with 10 different gate biases (Id = 10 − 100 mA/mm)
11/08/2017 Yogesh S. Chauhan, IIT Kanpur 74
Lines – ModelSymbols – Measured Data
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Y-Parameters
• The peaks and dips and their bias dependence is a manifestation of the interaction between the intrinsic capacitances and the extrinsic inductances.
• The values of bus-inductances can be fine-tuned to fit the peaks/dips in measured and modeled extrinsic-level Y-parameters.
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RF Parameter Extraction Flow
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Power Amplifier Design Goals
16
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Helps us:
• Determine Optimum load impedance for maximum Pout and PAE performance
• Matching networks
• Understand tradeoffs!
Load Pull Technique
[M. S. Hashmi et. al, IEEE Instrum. Meas. Mag., 16 (2), Feb., (2013)]
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Load-Pull Schematic & Overlays
S. A. Ahsan, et. al, IEEE Trans. Microwave Theory Tech, 2017.11/08/2017 Yogesh S. Chauhan, IIT Kanpur 79
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Load Pull Contours
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Harmonic Balance Power Sweeps
S. A. Ahsan, et. al, IEEE Trans. Microwave Theory Tech, 2017.11/08/2017 Yogesh S. Chauhan, IIT Kanpur 81
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Model Quality
82Yogesh S. Chauhan, IIT Kanpur11/08/2017
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Toshiba device Id and derivatives
Full device (simulation)
Yogesh S. Chauhan, IIT Kanpur 83
ID
ID’ = GX
ID’’ = GX’ ID’’’=GX’’
Smooth and continuous Id and its derivatives
11/08/2017
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Toshiba deviceIntrinsic device (simulation)
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Intrinsic device passes Gummel Symmetry Test
11/08/2017
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Characterization and Parameter Extraction for RFMD RF 3931 Device
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(Devices received from ISRO)
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Summary• Physics-based fully analytical model for the GaN
HEMTs• Excellent agreement with the measured data at
different temperatures for different channel length devices
• Model is implemented in the Verilog - A code • Tested on Agilent ADS, Synopsys HSPICE and
Cadence’s Spectre simulators• In final phase of industry standardization at CMC
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My Group and Nanolab
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Current members – 30• Postdoc – 5• Ph.D. – 17 • Three PhD graduated
– Postdocs in UC Berkeley and U. Bordeaux France
2017 2016 2015 2014 2013 2012
Books 1 1Journal 20 18 9 5 3 3Conference 8 30 30 8 4 6
Funding in last 5 years:> Rs. 8.5 Crore
Device Characterization Lab‐ Pulsed IV/RF ‐ PNA‐X 43.5GHz‐ High Power IV
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GaN-HEMT Journal Publications1. S. A. Ahsan, A. Pampori, S. Ghosh, S. Khandelwal, and Y. S. Chauhan, "A New Small-signal Parameter
Extraction Technique for large gate-periphery GaN HEMTs", in IEEE Microwave and Wireless Components Letters, Vol. 27, Issue 10, Oct. 2017.
2. S. A. Ahsan, S. Ghosh, S. Khandelwal, and Y. S. Chauhan, "Physics-based Multi-bias RF Large-Signal GaN HEMT Modeling and Parameter Extraction Flow", in IEEE Journal of the Electron Devices Society, Vol. 5, Issue 5, Sept. 2017.
3. S. A. Ahsan, S. Ghosh, S. Khandelwal, and Y. S. Chauhan, "Pole-Zero Approach to Analyze and Model the Kink in Gain-Frequency Plot of GaN HEMTs", IEEE Microwave and Wireless Components Letters, Vol. 27, Issue 3, Mar. 2017.
4. S. A. Ahsan, S. Ghosh, S. Khandelwal, and Y. S. Chauhan, "Analysis and Modeling of Cross-Coupling and Substrate Capacitance in GaN HEMTs for Power-Electronic Applications", IEEE Transactions on Electron Devices (Special Issue), Vol. 64, Issue 3, Mar. 2017.
5. A. Dasgupta and Y. S. Chauhan, "Modeling of Induced Gate Thermal Noise in HEMTs", IEEE Microwave and Wireless Components Letters, Vol. 26, Issue 6, June 2016.
6. S. A. Ahsan, S. Ghosh, A. Dasgupta, K. Sharma, S. Khandelwal, and Y. S. Chauhan, "Capacitance Modeling in Dual Field Plate Power GaN HEMT for Accurate Switching Behaviour", IEEE Transactions on Electron Devices, Vol. 63, Issue 2, Feb. 2016.
7. A. Dasgupta, S. Khandelwal, and Y. S. Chauhan, "Surface potential based Modeling of Thermal Noise for HEMT circuit simulation", IEEE Microwave and Wireless Components Letters, Vol. 25, Issue 6, June 2015.
8. S. Ghosh, A. Dasgupta, S. Khandelwal, S. Agnihotri, and Y. S. Chauhan, "Surface-Potential-Based Compact Modeling of Gate Current in AlGaN/GaN HEMTs", IEEE Transactions on Electron Devices, Vol. 62, Issue 2, Feb. 2015.
9. A. Dasgupta, S. Khandelwal, and Y. S. Chauhan, "Compact Modeling of Flicker Noise in HEMTs", IEEE Journal of Electron Devices Society, Vol. 2, Issue 6, Nov. 2014.
10. S. Khandelwal, C. Yadav, S. Agnihotri, Y. S. Chauhan, A. Curutchet, T. Zimmer, J.-C. Dejaeger, N. Defranceand T. A. Fjeldly, "A Robust Surface-Potential-Based Compact Model for GaN HEMT IC Design", IEEE Transactions on Electron Devices, Vol. 60, Issue 10, Oct. 2013.
11. S. Khandelwal, Y. S. Chauhan, and T. A. Fjeldly, "Analytical Modeling of Surface-Potential and Intrinsic Charges in AlGaN/GaN HEMT Devices", IEEE Transactions on Electron Devices, Vol 59, Issue 8, Oct. 2012.
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GaN-HEMT Conference Publications1. S. Khandelwal, S. Ghosh, S. A. Ahsan and Y. S. Chauhan, "Dependence of GaN HEMT AM/AM and AM/PM Non-Linearity on AlGaN Barrier Layer Thickness", IEEE Asia Pacific Microwave Conference (APMC), Kuala Lumpur,
Malaysia, Nov. 2017.
2. S. A. Ahsan, S. Ghosh, S. Khandelwal and Y. S. Chauhan, "Surface-potential-based Gate-periphery-scalable Small-signal Model for GaN HEMTs", IEEE Compound Semiconductor IC Symposium (CSICS), Miami, USA, Oct. 2017.
3. S. Ghosh, S. A. Ahsan, A. Dasgupta, S. Khandelwal, and Y. S. Chauhan, "GaN HEMT Modeling for Power and RF Applications using ASM-HEMT", IEEE International Conference on Emerging Electronics (ICEE), Mumbai, India, Dec. 2016.
4. S. Ghosh, A. Dasgupta, A. K. Dutta, S. Khandelwal, and Y. S. Chauhan, "Physics based Modeling of Gate Current including Fowler-Nordheim Tunneling in GaN HEMT", IEEE International Conference on Emerging Electronics (ICEE), Mumbai, India, Dec. 2016.
5. S. A. Ahsan, S. Ghosh, S. Khandelwal, and Y. S. Chauhan, "Statistical Simulation for GaN HEMT Large Signal RF performance using a Physics-based Model", IEEE International Conference on Emerging Electronics (ICEE), Mumbai, India, Dec. 2016.
6. A. Dasgupta, S. Ghosh, S. A. Ahsan, S. Khandelwal, N. Defrance, and Y. S. Chauhan, "Modeling DC, RF and Noise behavior of GaN HEMTs using ASM-HEMT Compact Model", IEEE International Microwave and RF Conference (IMaRC), Delhi, India, Dec. 2016.
7. S. A. Ahsan, S. Ghosh, A. Dasgupta, S. Khandelwal, and Y. S. Chauhan, "ASM-HEMT: Advanced SPICE Model for Gallium Nitride High Electron Mobility Transistors", International Conference of Young Researchers on Advanced Materials (ICYRAM), Bangalore, India, Dec. 2016.
8. S. Ghosh, S. A. Ahsan, S. Khandelwal and Y. S. Chauhan, "Modeling of Source/Drain Access Resistances and their Temperature Dependence in GaN HEMTs", IEEE Conference on Electron Devices and Solid-State Circuits (EDSSC), Hong Kong, Aug. 2016.
9. S. A. Ahsan, S. Ghosh, S. Khandelwal and Y. S. Chauhan, "Modeling of Kink-Effect in RF Behaviour of GaN HEMTs using ASM-HEMT Model", IEEE Conference on Electron Devices and Solid-State Circuits (EDSSC), Hong Kong, Aug. 2016.
10. R. Nune, A. Anurag, S. Anand and Y. S. Chauhan, "Comparative Analysis of Power Density in Si MOSFET and GaN HEMT based Flyback Converters", IEEE International Conference on Compatibility and Power Electronics, Bydgoszcz, Poland, June 2016.
11. S. Agnihotri, S. Ghosh, A. Dasgupta, A. Ahsan, S. Khandewal, and Y. S. Chauhan, "Modeling of Trapping Effects in GaN HEMTs", IEEE India Conference (INDICON), New Delhi, India, Dec. 2015.
12. S. Ghosh, S. Agnihotri, S. A. Ahsan, S. Khandelwal, and Y. S. Chauhan, "Analysis and Modeling of Trapping Effects in RF GaN HEMTs under Pulsed Conditions", International Workshop on Physics of Semiconductor Devices (IWPSD), Bangalore, India, Dec. 2015.
13. S. Agnihotri, S. Ghosh, S. Khandelwal, and Y. S. Chauhan, "Impact of Gate Field Plate on DC, C-V, and Transient Characteristics of Gallium Nitride HEMTs", International Workshop on Physics of Semiconductor Devices (IWPSD), Bangalore, India, Dec. 2015.
14. K. Sharma, S. Ghosh, A. Dasgupta, S. A. Ahsan, S. Khandelwal, and Y. S. Chauhan, "Capacitance Analysis of Field Plated GaN HEMT", International Workshop on Physics of Semiconductor Devices (IWPSD), Bangalore, India, Dec. 2015.
15. S. A. Ahsan, S. Ghosh, J. Bandarupalli, S. Khandelwal, and Y. S. Chauhan, "Physics based large signal modeling for RF performance of GaN HEMTs", International Workshop on Physics of Semiconductor Devices (IWPSD), Bangalore, India, Dec. 2015.
16. S. Khandelwal, S. Ghosh, Y. S. Chauhan, B. Iniguez, T. A. Fjeldly and C. Hu, "Surface-Potential-Based RF Large Signal Model for Gallium Nitride HEMTs", IEEE Compound Semiconductor IC Symposium (CSICS), New Orleans, USA, Oct. 2015.
17. S. A. Ahsan, S. Ghosh, K. Sharma, A. Dasgupta, S. Khandelwal, and Y. S. Chauhan, "Capacitance Modeling of a GaN HEMT with Gate and Source Field Plates", IEEE International Symposium on Compound Semiconductors (ISCS), Santa Barbara, USA, June 2015.
18. A. Dasgupta and Y. S. Chauhan, "Surface Potential Based Modeling of Induced Gate Thermal Noise for HEMTs", IEEE International Symposium on Compound Semiconductors (ISCS), Santa Barbara, USA, June 2015.
19. S. Khandelwal, Y. S. Chauhan, B. Iniguez, and T. Fjeldly, "RF Large Signal Modeling of Gallium Nitride HEMTs with Surface-Potential Based ASM-HEMT Model", IEEE International Symposium on Compound Semiconductors (ISCS), Santa Barbara, USA, June 2015. (Invited)
20. A. Dasgupta, S. Ghosh, S. Khandelwal, and Y. S. Chauhan, "ASM-HEMT: Compact model for GaN HEMTs", IEEE Conference on Electron Devices and Solid-State Circuits (EDSSC), Singapore, June 2015.
21. K. Sharma, A. Dasgupta, S. Ghosh, S. A. Ahsan, S. Khandelwal, and Y. S. Chauhan, "Effect of Access Region and Field Plate on Capacitance behavior of GaN HEMT", IEEE Conference on Electron Devices and Solid-State Circuits (EDSSC), Singapore, June 2015.
22. S. Ghosh, K. Sharma, S. Khandelwal, S. Agnihotri, T. A. Fjeldly, F. M. Yigletu, B. Iniguez, and Y. S. Chauhan, "Modeling of Temperature Effects in a Surface-Potential Based ASM-HEMT model", IEEE International Conference on Emerging Electronics (ICEE), Bangalore, India, Dec. 2014.
23. S. Agnihotri, S. Ghosh, A. Dasgupta, S. Khandewal, and Y. S. Chauhan, "A Surface Potential based Model for GaN HEMTs", IEEE PrimeAsia, Visakhapatnam, Dec. 2013. (Gold Leaf Certificate)11/08/2017 Yogesh S. Chauhan, IIT Kanpur 89