Table Of ContentEngineering Materials and Processes
Series Editor
ProfessorBrianDerby,ProfessorofMaterialsScience
ManchesterMaterialsScienceCentre,GrosvenorStreet,ManchesterM17HS,UK
Other titles published in this series:
FusionBondingofPolymerComposites
C.AgeorgesandL.Ye
CompositeMaterials
D.D.L.Chung
Titanium
G.Lu¨tjeringandJ.C.Williams
CorrosionofMetals
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CorrosionandProtection
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IntelligentMacromoleculesforSmartDevices
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MicrostructureofSteelsandCastIrons
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PhaseDiagramsandHeterogeneousEquilibria
B.Predel,M.HochandM.Pool
ComputationalMechanicsofCompositeMaterials
M.Kamin´ski
MaterialsforInformationTechnology
E.Zschech,C.WhelanandT.Mikolajick
PublicationdueJuly2005
Thermoelectricity
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ComputerModellingofSinteringatDifferentLengthScales
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ComputationalQuantumMechanicsforMaterialsEngineers
L.Vitos
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FuelCellTechnology
N.Sammes
PublicationdueJanuary2006
Stephen J. Pearton, Cammy R. Abernathy
and Fan Ren
Gallium Nitride
Processing for
Electronics, Sensors
and Spintronics
With 241 Figures
Stephen J. Pearton, PhD
Department of Materials Science and Engineering, P.O. Box 116400,
University of Florida, Gainesville, FL 32611, USA
Cammy R. Abernathy, PhD
Department of Materials Science and Engineering, P.O. Box 116400,
University of Florida, Gainesville, FL 32611, USA
Fan Ren, PhD
Department of Chemical Engineering, P.O. Box 116005, University of Florida,
Gainesville, FL 32611, USA
BritishLibraryCataloguinginPublicationData
Pearton,S.J.
Galliumnitrideprocessingforelectronics,sensorsand
spintronics.—(Engineeringmaterialsandprocesses)
1.Semiconductors 2.Galliumnitride 3.Detectors—
Technologicalinnovations
I.Title II.Abernathy,C.R. III.Ren,F.
621.3′8152
ISBN-10:1852339357
LibraryofCongressControlNumber:2005926297
EngineeringMaterialsandProcessesISSN1619-0181
ISBN-10:1-85233-935-7
ISBN-13:978-1-85233-935-7
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Preface
The GaN-based materials system has provided over a decade of surprises,
from the initial breakthroughs with visible light-emitting diodes (LEDs) to
laser diodes, solar-blind ultraviolet (UV) detectors to microwave power
electronics and then to solid-state UV light sources and white lighting.
Even recently, the bandgap of InN was determined to be closer to 0.7 eV
rather than the value of 1.9 eV accepted for many years. The areas men-
tioned above have been extensively covered in other books and in the lit-
erature. The purpose of this volume is to cover some of the newer areas of
research and development for GaN, such as sensors, megawatt electronics,
and gate dielectrics for transistors and spin-transport electronics (or spin-
tronics), along with advances in processing of the material. GaN-based
visible LEDs and laser diodes are already commercialized for a variety of
lighting and data storage applications. This materials system is also
showing promise for microwave and high-power electronics intended for
radar, satellite, wireless base stations, and utility grid applications, for
biological detection systems, and for a new class of spintronics in which
the spin of charge carriers is exploited. The explosive increase in interest
in the AlGaInN family of materials in recent years has been fueled by the
application of blue–green–UV LEDs in full-color displays, traffic lights,
automotive lighting, and general room lighting using so-called white LEDs
[1]. In addition, blue–green laser diodes can be used in high storage-
capacity digital versatile disks (DVDs) systems. AlGaN-based photode-
tectors are also useful for solar-blind UV detection and have applications
as flame sensors for control of gas turbines or for detection of missiles.
There are currently major development programs in the United States for
three newer applications for GaN-based materials and devices, namely:
i. UV optical sources capable of operation down to 280 nm for use
in airborne chemical and biological sensing systems, allowing di-
rect multi-wavelength spectroscopic identification and monitoring
of UV-induced reactions.
ii. Power amplifiers and monolithic microwave integrated circuits
(MMICs) for use in high-performance radar units and wireless
broadband communication links and ultra-high-power (>1 MW)
switches for control of distribution on electricity grid networks.
v
vi Preface
iii.Room-temperature, ferromagnetic semiconductors for use in elec-
trically controlled magnetic sensors and actuators, high-density,
ultra-low-power memory and logic, spin-polarized light emitters
for optical encoding, advanced optical switches and modulators,
and devices with integrated magnetic, electronic, and optical func-
tionality. There is currently a lot of interest in the science and po-
tential technological applications of spintronics, in which the spin
of charge carriers (electrons or holes) is exploited to provide new
functionality for microelectronic devices. The phenomena of giant
magnetoresistance and tunnelling magnetoresistance have been
exploited in all-metal or metal–insulator–metal magnetic systems
for read/write heads in computer hard drives, magnetic sensors,
and magnetic random access memories. The development of mag-
netic semiconductors with practical ordering temperatures could
lead to new classes of device and circuits, including spin transis-
tors, ultra-dense non-volatile semiconductor memory, and optical
emitters with polarized output.
In addition, there is increasing interest in use of GaN-based structures
for increasing the sensitivity, selectivity, and reliability of sensor devices
while keeping their fabrication at low cost. There is still a lack of funda-
mental understanding of the physical/chemical/biological phenomena at
the origin of the sensing mechanism in most cases. The GaN has potential
for chemical sensors and field effect transistor (FET) devices, magnetic
sensors, radiation sensors, acoustic sensors, mechanical sensors, and bio-
sensors.
It is hoped that this volume will prove useful to researchers entering
these new areas.
Acknowledgments
We wish to thank our many collaborators over the past few years, includ-
ing G. Thaler, B.P. Gila, R. Frazier, A.H. Onstine, J. Kim, S. Kim, B.S.
Kang, A.P. Zhang, X.A. Cao, J.W. Johnson, B. Luo, K. Baik, K. Ip, R.
Khanna, D.P. Norton, J.M. Zavada, R.G. Wilson, J. Lin, M.E. Law, K.S.
Jones, W.M. Chen, I.A. Buyanova, A.Y. Polyakov, Y. Irokawa, J.R.
LaRoche, M.E. Overberg, R.J. Shul, A.G. Baca, J.C. Zolper, K.E. Waldrip,
M. Stavola, S.N.G. Chu, M.W. Cole, W.S. Hobson, J.W. Lee, and C. Var-
tuli.
Preface vii
References
1. Nakamura S, Pearton SJ, Fasal G, The Blue Laser Diodes (Springer,
Berlin, 2000)
Gainesville, Florida, USA Stephen J. Pearton
Cammy R. Abernathy
Fan Ren
Contents
Preface...........................................................................................................v
1 Advanced Processing of Gallium Nitride for Electronic Devices..............1
1.1 Abstract ............................................................................................1
1.2 Introduction......................................................................................2
1.3 Results and Discussion...................................................................16
1.3.1 Ultra-High-Temperature Activation of Implant Doping
in Gallium Nitride................................................................16
1.3.1.1 High-Temperature Annealing and Aluminum
Nitride Encapsulation..............................................17
1.3.1.2 n-Type Implant Doping............................................22
1.3.1.3 p-Type Implant Doping............................................25
1.3.1.4 Dopant Redistribution..............................................26
1.3.1.5 Residual Damage.....................................................31
1.4 Implant Isolation.............................................................................32
1.4.1 Oxygen Implantation for Selective Area Isolation...............34
1.4.2 Creation of High-Resistivity Gallium Nitride by
Ti, Iron, and Chromium Implantation..................................38
1.5 Electrical Contacts to Gallium Nitride...........................................41
1.5.1 Effects of Interfacial Oxides on Schottky Contact...............44
1.5.2 Interfacial Insulator Model...................................................49
1.5.3 Thermally Stable Tungsten-Based Ohmic Contact...............51
1.5.4 Behavior of Tungsten and Tungsten Silicide
Contacts on p-Gallium Nitride.............................................54
1.6 Dry Etch Damage in Gallium Nitride.............................................60
1.6.1 Plasma Damage in n-Gallium Nitride...................................61
1.6.2 Effect of Etching Chemistries on Damage............................66
1.6.3 Thermal Stability of Damage................................................71
1.6.4 Plasma Damage in p-Gallium Nitride...................................75
1.6.5 Thermal Stability of Damage................................................80
1.6.6 Determination of Damage Profile in Gallium Nitride..........82
1.7 Conclusions and Future Trends......................................................86
References...................................................................................................89
ix
x Contents
2 Dry Etching of Gallium Nitride and Related Materials...........................97
2.1 Abstract...........................................................................................97
2.2 Introduction....................................................................................97
2.3 Plasma Reactors..............................................................................97
2.3.1 Reactive Ion Etching.............................................................98
2.3.2 High-Density Plasmas.........................................................100
2.3.3 Chemically Assisted Ion Beam Etching.............................101
2.3.4 Reactive Ion Beam Etching................................................102
2.3.5 Low-Energy Electron Enhanced Etching............................103
2.4 Plasma Chemistries.......................................................................104
2.4.1 Chlorine-Based Plasmas.....................................................104
2.4.2 Iodine- and Bromine-Based Plasmas..................................116
2.4.3 Methane–Hydrogen–Argon Plasmas..................................121
2.5 Etch Profile and Etched Surface Morphology..............................122
2.6 Plasma-Induced Damage..............................................................124
2.6.1 n-Gallium Nitride................................................................126
2.6.2 p-Gallium Nitride................................................................133
2.6.3 Schottky Diodes..................................................................141
2.6.4 p-n Junctions.......................................................................148
2.7 Device Processing.........................................................................152
2.7.1 Microdisk Lasers.................................................................152
2.7.2 Ridge Waveguide Lasers....................................................153
2.7.3 Heterojunction Bipolar Transistors.....................................157
2.7.4 Field Effect Transistors.......................................................161
2.7.5 Ultroviolet Detectors...........................................................166
References.................................................................................................169
3 Design and Fabrication of Gallium Nitride High-Power Rectifiers.......179
3.1 Abstract.........................................................................................179
3.2 Introduction..................................................................................179
3.3 Background...................................................................................180
3.3.1 Temperature Dependence of Bandgap................................180
3.3.1.1 Gallium Nitride......................................................180
3.3.1.2 6H-SiC...................................................................181
3.3.2 Effective Density of States.................................................182
3.3.3 Intrinsic Carrier Concentration...........................................182
3.3.4 Incomplete Ionization of Impurity Atoms..........................183
3.3.5 Mobility Models.................................................................184
3.3.5.1 Analytical Mobility Model.....................................184
3.3.5.2 Field-Dependent Mobility Model..........................185
3.3.6 Generation and Recombination..........................................186
3.3.6.1 Shockley–Read–Hall Lifetime...............................186
Contents xi
3.3.6.2 Auger Recombination............................................186
3.3.7 Reverse Breakdown Voltage..............................................186
3.3.8 On-State Resistance............................................................191
3.4 Edge Termination Design.............................................................195
3.4.1 Field Plate Termination......................................................195
3.4.2 Junction Termination..........................................................198
3.5 Comparison of Schottky and p-n Junction Diodes.......................201
3.5.1 Reverse Bias.......................................................................201
3.5.2 Forward Bias.......................................................................201
3.6 High Breakdown Lateral Diodes..................................................204
3.7 Bulk Diode Arrays....................................................................... 207
3.8 Conclusions..................................................................................210
References.................................................................................................211
4 Chemical, Gas, Biological, and Pressure Sensing..................................213
4.1 Abstract.........................................................................................213
4.2 Introduction..................................................................................214
4.3 Sensors Based on AlGaN–GaN Heterostructures.........................219
4.3.1 Gateless AlGaN–GaN High Electron Mobility
Transistor Response to Block Co-Polymers......................219
4.3.2 Hydrogen Gas Sensors Based on AlGaN–GaN-Based
Metal-Oxide Semiconductor Diodes..................................222
4.3.3 Hydrogen-Induced Reversible Changes in Sc O –
2 3
AlGaN–GaN High Electron Mobility Transistors.............226
4.3.4 Effect of External Strain on Conductivity of AlGaN–
GaN High Electron Mobility Transistors...........................230
4.3.5 Pressure Sensor Fabrication................................................236
4.3.6 Selective-Area Substrate Removal.....................................239
4.3.7 Biosensors Using AlGaN–GaN Heterostructures...............240
4.3.8 Surface Acoustic Wave-Based Biosensors.........................245
4.4 Surface Acoustic Wave Device Fabrication.................................247
4.5 Surface Acoustic Wave Device for Gas Sensing..........................250
4.6 Flexural Plate Wave Device for Liquid Sensing..........................251
4.7 Surface Acoustic Wave Array......................................................251
4.8 Wireless Sensor Network and Wireless Sensor Array
Using Radio Frequency Identification Technology.....................252
4.9 Summary.......................................................................................255
References.................................................................................................255
5 Nitride-Based Spintronics......................................................................261
5.1 Abstract........................................................................................261
5.2 Introduction.................................................................................261
