Silvaco TCAD
Leader in Power Device TechnologyDevelopment

Silvaco TCAD for GaN
TechnologyProcess Simulation
Device Simulation
ExamplesCopyright │ ©2023 Silvaco, Inc.

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Victory Process GaN Simulation Overview
Virtualize your process flow to optimize and understand how the next generation power devices
should be fabricated• Full 2D/3D TCAD Process Solution• Build, debug, calibrate in fast 2D• Easy transition to realistic 3D for full 3Dtechnology design• Seamless integration into Device Simulation• Process simulation for GaN• Etch & Deposition• Stress• Implantation• Dopant Activation• Open Model Library and Material database• Allows for user customizability

Copyright │ ©2023 Silvaco, Inc.

GaN Tri-Gate Structure3Etch and Deposition for Next Generation Devices
Capturing material geometry faithfully ensures TCAD simulation matches the fab• GDSII driven TCAD, connecting fab to TCAD
• Import layout to use as masks for any process step

• Simple geometric models for fast simulating etch & deposition steps• Define etch/deposition thicknesses and a geometric model• Detailed physical models for deeper understanding of your process steps• Define deposition/etch rates for each material• Sticking factors, flux parameters• Useful for understand visibility effects

Copyright │ ©2023 Silvaco, Inc.

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Accurately Predict Stress Distribution in Process
Victory Process provides capabilities covering stress simulation
Stress analysis of arbitrary 2D/3D device structure•

Stress simulation for various crystalline and isotropic materials•

Generic 3D anisotropic stress simulation•Estimation of mobility enhancement factors by use ofpiezoresistivity model devices

Models for various sources of strain and stress•

Thermal mismatch between material layers•

Local lattice mismatch due to doping•

Initial deposit stress in specified regions•External (hydro-static) stress from capping layers•

Stress/strain generated in previous processing stepCopyright │ ©2023 Silvaco, Inc.

Compressive Stress from Nitride Layer inGaN HEMT Device
5Understand Implantation Details
Future GaN Devices will incorporate doping in new ways. Accurate implantation modeling will berequired• Monte Carlo Implantation• User-Definable Implant Properties• Substrate type/orientation, angle, dose and energy• Well calibrated stopping within crystal channels and random direction• Crystal Damage & Scattering due to damage accumulation• Empirical Methods to define doping in process• Doping profiles by analytical distribution function• Quickly add Gaussian doping• Doping profiles defined by external data files• Use SIMS profiles to build your TCAD process

Copyright │ ©2023 Silvaco, Inc.

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Victory Device for GaN Power Devices
Victory Device covers the breadth and depth of GaN device simulation needs
Simulate DC, AC and transient electrical simulation• Understand how your device performs in any scenario
Self-Heating Simulation• Gain insight into self-heating effects that influences electrical physics
Reliability and Radiation• Simulate device degradation due to electrical stress, as well as radiation effects (TID, DD, SEB)
MixedMode circuit/device simulation• Simulate TCAD devices within a SPICE circuit
User-customizable physical models & material parameters• Calibrate any simulated device to your experimental data
• Novel wide bandgap materials can be simulated by adjusting the physical parameters
Advance numerical solvers and methods• Multithreaded simulations and numerical extended precision available for the more difficult
simulations
Copyright │ ©2023 Silvaco, Inc.

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Calculate Essential Interface Charges
Heterojunction interfaces make GaN technology possible• Spontaneous and Piezo-Electric Polarization– Victory Device can automatically calculate the Spontaneous andPiezo-Electric Polarization Interface Charges• Quickly generate and understand the 2DEG in your device• Composition Dependent Physical Models– All models are composition dependent for AlGaN and other ternaryand quaternary material sets
• Band gap, Electron Affinity, Permittivity, Density of State Masses,Recombination, Heat capacity, Refractive Index• Analyze how composition may affect performance

Copyright │ ©2023 Silvaco, Inc.

2DEG formed inside Tri-Gate
GaN HEMT Device8Accurately Model Mobility in GaN
Using the correct mobility models are essential for simulating your device properly.
• High Field and Low Field Models forMobility– GaN Specific Mobility Models for Low Field andHigh Field– Low Field: Albrecht & Farahmand• Albrecht Model consist of 3 components that can becalibrated to fit your device• Farahmand Model is a Caughey-Thomas like model
Calibrated for Nitride material sets

– High Field: GaNSat• Simulate high-field effects such as negative
differential mobility with respect to the electric fieldCopyright │ ©2023 Silvaco, Inc.

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Vital Physical Models for GaN Power Devices
Victory Device can simulate all the important effects needed to fully simulate GaN power device
Incomplete Ionization of Impurities– Can directly or indirect effect mobility and other physical properties in device
Bulk and Interface State Models– Correctly model the defects in GaN that can degrades performance and can affect
DC/transient response
Leakage Current Models useful in GaN– Trap Assisted Schottky Tunnel– Variable Range Hopping

Copyright │ ©2023 Silvaco, Inc.

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Gallium Nitride Examples

Copyright │ ©2023 Silvaco, Inc.

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GaN HEMT - Process + Device

Multi-layer GaN structures simulated accurately to optimize device structure and performance

Vertical Cutline through Gate /AlGaN / GaN stack

Copyright │ ©2023 Silvaco, Inc.

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GaN HEMT - IV Characteristics

DC IdVg

Simulation of HEMT
showing DC Id-Vg & IdVd Family

Gate Voltage• Pulse IdVd shows reduction of current flow by
18% at Vd=5VCopyright │ ©2023 Silvaco, Inc.

DC IdVd

Drain Voltage

Drain Current

Simulation Comparing the DC IdVd and Transient
Pulse IdVd at Vg=0V

Drain Current

Drain Current (Log)

Drain Current

Multi-layer GaN structures simulated accurately to optimize device structure and performance

DC & Pulse IdVd
Drain Voltage

13GaN HEMT - Transient Pulse Simulation
Drain Current

Current Collapse

Current collapse caused
Transient Timeby bulk traps within theVoltage

buffer layer

Drain Voltage
Gate Voltage
Transient TimeCopyright │ ©2023 Silvaco, Inc.

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Novel 3D GaN Devices
Silvaco is embedded in tier-1 university research• Example from Virginia Tech University(Silvaco Collaborator)– Y. Ma et al., "Kilovolt Tri-Gate GaN Junction HEMTs with High Thermal

Stability," 2021 33rd International Symposium on Power Semiconductor
Devices and ICs (ISPSD), 2021

Copyright │ ©2023 Silvaco, Inc.

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Vertical GaN Superjunction HEMT Simulation
Based on Reference Paper - L. Zhongda, T.P. Chow,"Design and simulation of 5-20-kV GaN enhancementmode vertical superjunction HEMT", IEEE Trans.
Electron Dev, vol.60, no.10, 2013, pp.3230-3237.

Basic Device Sketch

2D TCAD Design

Copyright │ ©2023 Silvaco, Inc.

IdVd

BV

Simulation Results
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Lattice Heating Simulations
GIGA Module allows users to simulate self consistent electro-thermal physics
GaNFET device with/without top heat sink
• Device without heat sink shows significant

heating & degradation in device electricalperformance

GaNFET Device

IdVd
With Heat Sink

Freq Response

Without Heat Sink

Temperature Profiles During Operation
Effect of Self-heating on DC and RF characteristics with/without top heat sink
Copyright │ ©2023 Silvaco, Inc.

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Vertical GaN Devices
Current Aperture Vertical Electron Transistor (CAVET)
S. Chowdhury, M. H. Wong, B. L. Swenson, and U. K.
Mishra, "CAVET on bulk GaN substrates achieved with
MBE-regrown AlGaN/GaN layers to suppress dispersion",
IEEE Electron Device Letters, vol.33, Jan. 2012.

p-GaN

n- GaNn+ GaNUC Davis Experimental Data
Copyright │ ©2023 Silvaco, Inc.

Silvaco Simulations
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Silvaco is leading theway for next
generation Power
Device Technology
simulation

BCD
Power DiodeThyristor
IGBT

Copyright │ ©2023 Silvaco, Inc.

SiCDMOSTrenchMOSJBSGaN

Lateral HEMT
Vertical HEMTP-GaN Gate HEMTSilicon19