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Physics and Astronomy

57

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Springer Series in

MATERIALS SCIENCE

Editors: R. Hull R. M. Osgood, Jr. J. Parisi

The Springer Series in Materials Science covers the complete spectrum of materials physics, including fundamental principles, physical properties, materials theory and design. Recognizing the increasing importance of materials science in future device technologies, the book titles in this series reflect the state-of-the-art in understanding and controlling the structure and properties of all important classes of materials.

51 Microscopic and Electronic Structure of Point Defects in Semiconductors and Insulators Determination and Interpretation of Paramagnetic Hyperfine Interaction Editors: J. M. Spaeth and H. Overhof

52 Polymer Films with Embedded Metal Nanoparticles By A. Heilmann

53 Nanocrystalline Ceramics Synthesis and Structure By M. Winterer

54 Electronic Structure and Magnetism of Complex Materials Editors: D.J. Singh and A. Dimitrios

55 Quasicrystals An Introduction to Structure, Physical Properties and Applications Editors: J.-B. Suck, M. Schreiber, P. Haussler

56 Si02 in Si Microdevices ByM.Itsumi

57 Radiation Effects in Advanced Semiconductor Materials and Devices By C. Claeys and E. Simoen

Series homepage- http://www.springer.de/phys/books/ssms/

Volumes 1-50 are listed at the end of the book.

C. Claeys E. Simoen

Radiation Effects in Advanced Semiconductor Materials and Devices

With 331 Figures

Springer

Prof. Cor Claeys Dr. Eddy Simoen IMEC Leuven/Belgium, Kapeldreef 75, 3001 Leuven, Belgium

Series Editors: Prof. R. M. Osgood, Jr. Microelectronics Science Laboratory Department of Electrical Engineering Columbia University Seeley W. Mudd Building New York, NY 10027, USA

Prof. Robert Hull University of Virginia Dept. of Materials Science and Engineering Thornton Hall Charlottesville, VA 22903-2442, USA

ISSN 0933-33X

ISBN 978-3-642-07778-4

Library of Congress Cataloging-in-Publication Data

Claeys,C:

Prof. Dr. Jiirgen Parisi Universitat Oldenburg Fachbereich Physik Abt. Energie- und Halbleiterforschung Carl-von-Ossietzky-Str. 9-11 26129 Oldenburg, Germany

Radiation effects in Advanced Semiconductor Materials and Devices I C. Claeys; E. Simoen. - Berlin; Heidelberg; New York; Barcelona; Hongkong; London; Milan; Paris; Tokyo: Springer, 2002 (Springer series in materials science; v. 57) (Physics and astronomy online library) - Includes biographical references. ISBN 978-3-642-07778-4 ISBN 978-3-662-04974-7 (eBook) DOI 10.1007/978-3-662-04974-7

This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in other ways, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag Berlin Heidelberg GmbH.

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Preface

There is a growing tendency for using commercial state-of-the-art microelectronic components for space applications. This is driven, on the one hand, by the so­called custom-off-the-shelf (COTS) approach, where commercial components and circuits are increasingly replacing dedicated expensive radiation hardened elec­tronics. On the other hand, scaling of silicon technologies brings about an inherent hardening against permanent damage, as thin gate dielectrics become less and less prone to it. Furthermore, the use of smart or integrated sensors and MEMS will further stimulate the use of silicon microelectronics in space and other radiation environments, like CERN's future Large Hadron Collider. In fact, in the ultimate limit of scaling, complete systems-on-chip (SOC's) are expected to emerge, com­bining different technologies and new materials on the same substrate. Further­more, in order to meet the requirements of the International Technology Roadmap for Semiconductors (ITRS), scaling of the main technology (CMOS) will require the use of novel materials and processing steps. For example, SiGe epitaxy will be implemented more and more for high-speed telecom applications, replacing III-V materials. Novel gate dielectrics (high-k materials) and intermetallayer dielectrics (low-k) will be introduced. Ferroelectrics are becoming of growing interest for memory applications. Device isolation in upcoming technologies will no longer be achieved by LOCOS techniques but requires advanced schemes like Shallow Trench Isolation. For high-speed satellite communication and for on-chip commu­nication, the use of opto-electronics will strongly increase. At the moment, most of the components and systems are based on direct-gap 111-V materials, but there is intensive search for silicon-based and silicon-compatible optical interconnects. Powering of satellites is based on solar energy conversion using low-weight high­efficiency tandem solar cells. Currently, the system GaAs on Ge substrates is fmd­ing progressive application in satellites. The future use of so-called nano-satellites will trigger the implementation of state-of-the-art microelectronic components and >ystems.

It is clear from the above that these developments in the semiconductor indus­zy are not driven primarily with space applications or radiation hardness in mind. [t is felt, therefore, that there is a need to have a clear view of potential radiation iamage problems, even at an early stage of the development of the latest technol­)gy generations. This is not only important for the space community itself but can )e beneficial during the process/technology development as well. The reason is :hat during device or circuit fabrication more and more processing steps use an iggressive environment where irreversible radiation damage can occur. So a fun­iamental understanding of radiation damage mechanisms and degradation is not

VI Preface

only of use for the nuclear/space engineer, but may be helpful for the process en­gineer as well. This monograph is oriented in the first place towards post-graduate researchers who want to enter the field and wish to obtain a good overview of the radiation damage in semiconductor materials and advanced devices. A background in semiconductor and device physics and its interaction with radiation is assumed, although some basic concepts will be briefly summarized. Furthermore, whenever possible, an outlook towards future developments and experimental or modeling needs/shortcomings is provided so that even for the experts in the field, the book could provide significant added value.

The book contains 9 chapters and analyses radiation effects in a variety of semiconductor materials and devices. A kind of justification for the book and a brief discussion of the different radiation environments are addressed in Chap. 1. Information is also given about the component selection strategies for space appli­cations. The basic radiation damage mechanisms in semiconductor materials and devices form the subject of a second chapter. A good fundamental insight into ma­terial science and device physics is essential for a proper understanding of the fol­lowing chapters. Chapter 3 reviews the knowledge related to displacement damage in group IV semiconductor materials such as silicon, germanium and silicon­germanium alloys. Attention is mainly paid to the present understanding of the fundamental mechanisms involved. The potential and drawbacks of several char­acterisation techniques are outlined whenever appropriate. The device applications of these materials are discussed in later chapters. Due to its importance for both micro- and opto-electronics applications, a fourth chapter is devoted to GaAs. Ra­diation aspects of silicon bipolar technologies, including vertical bipolar junction transistors (BJTs), lateral transistors and SiGe heterojunction bipolar transistors (HBTs) are critically reviewed in Chap. 5. As already mentioned in the introduc­tion, the key microelectronic technology, which is also driving the activities for scaling down the minimum feature size, is based on CMOS. The corresponding radiation aspects are studied in Chap. 6. Important issues such as ultra-thin gate oxides, alternative gate dielectrics based on nitrided and reoxidised nitrided oxides and device isolation are covered. A special section deals with silicon-on-insulator (SOl) CMOS technologies, as they are no longer limited to niche markets but are also gaining more and more interest for commercial applications. GaAs-based field effect transistors, such as MESFETS and HEMTs and their radiation re­sponse are reported in Chap. 7, while the opto-electronic components for space are given attention in Chap. 8. Attention is also paid to different types of components, including light emitting diodes (LEDs), laser diodes, photodetectors and optocou­plers. Due to space restrictions not all potential advanced semiconductor materials and devices can be covered in the book. Therefore the last chapter only briefly ad­dresses some hot topics such as non-volatile memories, high-k dielectrics for 100 nm and beyond CMOS and SiC and gives an outlook on component requirements for future space applications.

As the advances in the field are appearing so fast, a book can only give the status at a certain moment in time. Therefore the aim was not to look for com­pleteness, but rather to lay a sound physical basis and to give a critical overview of the type of semiconductor materials and devices presently used for microelectron-

Preface VII

ics in a radiation environment and to focus attention on some emerging technolo­gies with a strong potential for use in future space missions.

Over the years a large number of scientists and researchers from all over the world have greatly contributed by their discussions and critical comments to en­large the knowledge of the authors in the radiation field. The authors are in the first place very grateful to all their past and present IMEC colleagues in the field for stimulating discussions over the years. A special word of thanks has to go to ESTEC who has financially supported the radiation research activities during the past 15 years. A large part of the book is based on numerous discussions with L. Adams, B. Johlander, R. Harboe-S0rensen and A. Mohammadzadeh. The authors also wish to acknowledge Ms. Kathleen Mertens for her support with the scanning of the figures.

Leuven, April 2002 Cor Claeys Eddy Simoen

Table of Content

Preface

List of Acronyms

List of Symbols

List of Greek Symbols

1 Radiation Environments and Component Selection Strategy _________________ _! 1.1 Introduction __________________________________________________________________________________ 1 1.2 Radiation Environments ______________________________ ------------------------- __________ 1

1.2.1 Space Environments _____________________________________________________________ 2 1.2.2 High-Energy Physics Experiments _________________________________________ _3 1.2.3 Nuclear Environment ____________________________________________________________ 4 1.2.4 Natural Environment ____________________________________________________________ 5 1.2.5 Processing-Induced Radiation ________________________________________________ 6

1.3 Component Selection Strategy ________________________________________________________ 6 1.4 Conclusion 8

2 Basic Radiation Damage Mechanisms in Semiconductor Materials and Devices ________________________________________________________________________ 9

2.1 Introduction __________________________________________________________________________________ 9 2.2 Fundamental Damage Mechanisms __________________________________________________ 9

2.2.1 Nomenclature ______________________________________________________________________ 9 2.2.2 Ionisation Damage _____________________________________________________________ 1 0 2.2.3 Displacement Damage ________________________________________________________ 12

2.3 Impact of Radiation Damage on Device Performance _______________________ 20 2.3.1 Ionisation Damage _____________________________________________________________ 20 2.3.2 Displacement Damage ________________________________________________________ 28

2.4 Spectroscopic Study of Microscopic Radiation Damage ____________________ 37 2.4.1 Electron Paramagnetic Resonance (EPR)___ ____________________________ 37 2.4.2 Deep Level Transient Spectroscopy (DLTS) __________________________ 43 2.4.3 Photoluminescence Spectroscopy (PL) __________________________________ 49

2.5 Conclusion 51

X Table of Content

3 Displacement Damage in Group IV Semiconductor Materials ___________________________________________________________________ 53 3.1 lntroduction ________________________________________________________________________________ 53 3.2 Displacement Damage in Silicon ____________________________________________________ 54

3.2.1 Radiation Defects in Silicon _________________________________________________ 54 3.2.2 Impact of Radiation Defects on Silicon Devices ______________________ 62 3.2.3 Substrate and Device Hardening ___________________________________________ 66 3.2.4 Summary Silicon Radiation Defects ______________________________________ 69

3.3 Displacement Damage in Germanium _____________________________________________ 70 3.3.1 Potential Applications of Ge _______________________________________________ _70 3.3.2 Cryogenic Irradiation of Ge _________________________________________________ 71 3.3.3 Room Temperature Irradiation of Ge ____________________________________ _74 3.3.4 Impact Radiation Damage on Ge Materials and

Device Properties _______________________________________________________________ 76 3.3.5 Summary Germanium Radiation Defects ______________________________ _77

3.4 Displacement Damage in SiGe Alloys ____________________________________________ 78 3.4.1 SiGe Material Properties and Applications ____________________________ _78

3.4.2 Radiation Damage in SiGe·------------------~-------------------------------83 3.4.3 Processing-Induced Radiation Damage in SiGe ______________________ 95 3.4.4 Radiation Damage in SiGe Devices ____________________________________ _103 3.4.5 Conclusions Radiation Damage in SiGe Alloys ____________________ 107

3.5 General Conclusions Group-IV Serniconductors ____________________________ 107

4 Radiation Damage in GaAs _____________________________________________________________ _109 4.1 lntroduction ______________________________________________________________________________ 109 4.2 Basic Notations and Definitions ___________________________________________________ 110 4.3 Native and Radiation-Induced Point Defects in GaAs _____________________ 111

4.3.1 Native Point Defects in GaAs _____________________________________________ 112 4.3.2 Basic Radiation Defects in GaAs ________________________________________ 114 4.3.3 Neutron and Ion Radiation-Induced Defects

in GaAs __________________________________________________________________________ 119 4.3.4 Processing-Induced Radiation Defects in GaAs ___________________ _122 4.3.5 Summary Radiation Defects in GaAs _________________________________ _126

4.4 Damage Factors and NIEL __________________________________________________________ 127 4.4.1 Carrier Removal and Mobility Degradation

inGaAs 127 4.4.2 Correlation between Resistance Damage

Factor and NIEL ______________________________________________________________ 132 4.4.3 Lifetime Damage Factor and NIEL _____________________________________ 133 4.4.4 Correlation with Microscopic Damage ________________________________ 135 4.4.5 Summary Damage Factors and NIEL in GaAs _____________________ _138

4.5 Impact on GaAs Devices ____________________________________________________________ 139 4.5.1 Schottky Barriers and Radiation Detectors __________________________ _139 4.5.2 GaAs Solar Cells _____________________________________________________________ _140

4.6 General Conclusions 143

Table of Content XI

5 Space Radiation Aspects of Silicon Bipolar Technologies __________________ 145 5.1 Introduction ______________________________________________________________________________ 145 5.2 Device Structures and Basic Radiation Effects _______________________________ 145

5.2.1 Device Structures and Definitions ______________________________________ _145 5.2.2 Radiation Damage Mechanisms _________________________________________ _147

5.3 Degradation in Vertical (n-p-n) BJTs ____________________________________________ 148 5.3.1 Phenomenology of Total Dose Damage ______________________________ _149 5.3.2 Basic Low Dose-Rate Degradation Mechanisms ____ ~ _____________ _153 5.3.3 Charge Separation in BJTs _______________________________________________ _157 5.3.4 Hardening Guidelines for Vertical BJTs _____________________________ _163 5.3.5 Hardening Assurance and Testing_ _____________________________________ _164 5.3.6 Bulk Damage in Vertical Transistors __________________________________ _164

5.4 Degradation in Lateral Transistors ________________________________________________ 167 5.4.1 Phenomenology _______________________________________________________________ 167 5.4.2 Physical Mechanisms and Modeling __________________________________ _170

5.5 Degradation in SiGe HBTs __________________________________________________________ 172 5.5.1 Degradation ofthe Static and Low-Frequency

Noise Characteristics ________ ..... ___________________ . _______________________ 172 5.5.2 Degradation of the RF Characteristics ________________________________ _178

5.6 Conclusions 179

6 Radiation Damage in Silicon MOS Devices ______________________________________ _181 6.1 lntroduction .............................................................................. 181 6.2 Impact of Scaling on the Radiation Response _________________________________ 182

6.2.1 Gate Length Dependence __________________________________________________ _183 6.2.2 Lateral Non-Homogeneous Damaging ________________________________ _185 6.2.3 Gate-Induced Drain Leakage (GIDL) _________________________________ _190

6.3 Processing Induced Radiation Damage Effects _______________________________ 192 6.3.1 Plasma Damage _______________________________________________________________ 193 6.3.2 Rapid Thermal Annealing (RTAL ____________________________________ _193 6.3.3 Gate Material and Contacting_ ___________________________________________ _197

6.4 Alternative Gate Dielectrics ........................................................ 199 6.4.1 Doped Oxides ...................................................... ____________ 199 6.4.2 Nitrided (NO) and Reoxidised Nitrided Oxides (RN0).. _______ 200 6.4.3 N20 or Nitrous Oxides ...................................................... 214

6.5 Ultra-Thin Oxides ____________________ .................................................. 216 6.5.1 Radiation-Induced Leakage Current (RILCL _______________________ 216 6.5.2 Radiation-Induced Soft Breakdown (RSB) ___________________________ 223 6.5.3 Single Event Gate Rupture ________________________________________________ 224 6.5.4 Reliability of Irradiated Thin Oxides ___________________________________ 225 6.5.5 Summary ........................................................................ 226

6.6 Device Isolation------------------------------------------------------------------------ 226 6.6.1 LOCOS Isolation _____________________________________________________________ 227 6.6.2 Shallow Trench Isolation ___________________________________________________ 229

6.7 Silicon-on-Insulator CMOS Technology _______________________________________ 232

XII Table of Content

6.7.1 Silicon-on-Sapphire (SOS) ________________________________________________ 234 6.7.2 Silicon-on-Insulator (SOl) Technologies ______________________________ 236 6.7.3 Radiation Hardness of SOl Technologies _____________________________ 239

6.8 Conclusions 243

7 GaAs Based Field Effect Transistors for Radiation-Hard Applications _________________________________________________________ 245

7.1 Introduction 245 7.2 Material Related Issues and Device

Structures and Operation _____________________________________________________________ 245 7.2.1 Defects in AIGaAs Layers _________________________________________________ 246 7.2.2 MESFET Structure and Operation ______________________________________ 246 7.2.3 HEMT Structure and Operation __________________________________________ 249

7.3 Radiation Damage and Hardening in GaAs MESFETs ____________________ 252 7.3.1 Degradation of the Basic FET Parameters ____________________________ 252 7.3.2 Low-Frequency Noise and Defect Related Effects _________________ 259 7.3.3 Circuit Related Degradation _______________________________________________ 263

7.4 Radiation Damage and Hardening in HEMTs ________________________________ 266 7.4.1 Degradation of the Basic Parameters ___________________________________ 266 7.4.2 Low-Energy Electron Effects on 2-DEG Properties _______________ 277 7.4.3 Circuit Degradation Aspects ______________________________________________ 278

7.5 Conclusions 280

8 Opto-Electronic Components for Space ___________________________________________ 281 8.1 Introduction ______________________________________________________________________________ 281 8.2 Opto-Electronic Components _______________________________________________________ 281

8.2.1 Light Emitting Diodes (LEDs) and Laser Diodes (LDs) _________ 281 8.2.2 Photodetectors _________________________________________________________________ 287 8.2.3 Optocouplers ___________________________________________________________________ 289

8.3 Basic Radiation Effects and Material Issues ___________________________________ 290 8.3.1 Impact oflrradiation on Optical Material Properties ______________ 290 8.3.2 Radiation Defects and Material Aspects in

Ternary Compounds _________________________________________________________ 302 8.3.3 Damage Factors and NIEL _________________________________________________ 308

8.4 Radiation Effects in Opto-Electronic Components __________________________ 312 8.4.1 Light Emitting Diodes and Laser Diodes ____________________________ _312 8.4.2 Photodetectors ________________________________________________________________ _320 8.4.3 Optocouplers ___________________________________________________________________ 327

8.5 Conclusions 330

9 Advanced Semiconductor Materials and Devices- Outlook ____________ 331 9.1 Introduction ____________________________________________________________________________ 331 9.2 Non-Volatile Memories ____________________________________________________________ 331

9.2.1 Flash Memories------------------------------------------------------------ 332 9.2.2 Ferroelectric Memories (FeRAMs) ___________________________________ 335 9.2.3 Conclusions ___________________________________________________________________ 336

Table of Content XIII

9.3 High-k Gate Dielectrics ______________________________________________________________ 336

9.4 Radiation Effects in SiC -------------------------------------------------------------339 9.4.1 SiC Material Properties and Analysis __________________________________ 340 9.4.2 Intrinsic and Radiation Defects in SiC ________________________________ _341 9.4.3 Macroscopic Damage in SiC Devices _________________________________ _346 9.4.4 Ionisation Damage in SiC MOSFETs and MESFETs ____________ _347

9.4.5 Summary ------------------------------------------------------------------------348 9.5 Conclusion and Outlook 350

References ___________________________________________________________________________________________ 351

List of Symbols

c c Ccs Cn

Cp

Cox D D* Dh DH DI D;t

Dn dn Dot

Dp ds D!h dE/d E Ec Ed Ee Eeh EF Efc Eo Eh E;

:device area (cm2)

: emitter area of a bipolar junction transistor (1J.m2)

: extrinsic base area of a bipolar transistor (1J.m2)

:carrier removal rate constant (cm2)

: lattice constant (A) :hopping conductivity parameter (K114)

:hole trapping yield (cm-3)

:mobility degradation damage constant (cm2)

: speed of light (3x108 rnls) : capacitance (F) : base-collector capacitance (pF) :capture rate for electr_ons (cm3/s) :capture rate for holes (em%) : oxide capacitance per unit area (F/cm2)

: dose (rad or Gray) : responsivity of a photo-detector (AIW) : hole diffusivity (cm2/s) :density of states in the 2-dimensional electron gas (cm-2Y 1)

: diffusivity of the self-interstitial I (cm2/s) :density of interface traps (eV-1cm-2)

:electron diffusivity (em%) : channel depth of a MESFET (nm) :density of oxide traps (eV-1cm-2)

: hole diffusivity (cm2/s) : spacer layer thickness of a HEMT (nm) :threshold implantation dose for implant isolation (cm-2)

x: stopping power (MeV cm2/g) : particle energy (ke V, MeV) : minimum of the conduction band ( e V) : threshold energy for atomic displacement ( e V) :electron confinement energy in a QW (meV) :electron-hole pair ionisation threshold (eV) : Fermi energy ( e V) :cluster formation energy (eV) :band gap (eV) : heavy hole confinement energy in a QW (me V) : intrinsic level ( e V)

XVI List of Symbols

emax

Eph

E, Er Ev Ex F FF Fcrit

Fi

Fk fm(x) /max Fox /y fr g go Gchan

gd GHo

8ij

8m GNEx GN,N h 11 H H he io Is hi as

Ic /o

foo losAr fe /p Ia ho lmg

IN fop

: ion energy (ke V) : maximum energy transmitted to the target nuclei (ke V) :emission rate window (DLTS) (s-1)

: phonon energy (ke V, MeV) : average recoil energy ( e V) : trap energy level ( e V) : maximum of the valence band ( e V) : binding energy of the free exciton ( e V) : electric field (V /em) : fill factor of a solar cell :critical field for single event gate oxide rupture (V/cm) : electric field at the interface of a heterojunction FET (V /em) : critical gate oxide field for radiation-induced leakage current (V /em) :mismatch parameter of a Si1_xGex alloy : maximum oscillation frequency (GHz) :oxide field (V/cm) :hole yield : cutoff frequency (GHz) : degeneracy factor : free electron g factor (2.002319) : channel conductance of a MOSFET (S) : channel conductance OI0 /8V os of a FET (S) :fitting parameter for the drain current of a MESFET (V-1)

: spin second rank tensor : transconductance 810 /8V as of a FET (S) :extrinsic Gummel number of a bipolar transistor (s/cm4)

:intrinsic Gummel number of a bipolar transistor (s/cm4)

:Planck's constant (=6.62617x10-34 J s) :reduced Planck's constant h/27t (=1.05458x10-34 J s) : magnetic field : magnitude of magnetic field (G) : critical thickness of an epitaxial layer (nm) :inclination of a satellite orbit with respect to the Earth's axis (degrees) : base current of a bipolar transistor (A) : operation current of a LD or a LED (rnA) : collector current of a bipolar transistor (A) :drain or channel current (A) : dark current of a photodiode (A) : saturation drain current of a FET (A) : excess gate current due to radiation-induced leakage current (A) : forward current (A) :gate current (A) : photocurrent of a photodiode (A) : midgap current (A) :magnetic moment of the nucleus (vector) : operation current of a laser or light emitting diode (rnA)

List of Symbols XVII

lpL : photoluminescence intensity (a.u.) lR :reverse current (A) lRsB : excess gate current due to radiation-induced soft breakdown (A) lsc : short circuit current of a solar cell (A) h : threshold current (A) l 1h : threshold current for lasing action (A) le : excess gate current density (A/cm2)

lEx : extrinsic base current density (A/cm2)

IF : forward diode current density (A/cm2)

fa : gate current density (A/cm2)

h : reverse diode current density (A/cm2)

J+,J- : hole (+),electron (-)current density (A/cm2)

k :Boltzmann's constant (1.38066x10-23 J/K) K :damage factor (a.u.) Kfl :damage factor for the static current gain of a bipolar transistor (cm2)

KB :boron deactivation damage factor (cm-1)

K00 :dark current damage factor of a photodiode (A cm2/particle) K1 :leakage current damage factor (A cm2/particle) K10 :laser diode threshold current damage factor (cm2/particle) K1 :leakage current density damage factor (A/particle) KL :diffusion length damage factor KLo : photocurrent damage factor of a photodiode (A cm2/particle) K11 :mobility damage factor (Vs) Kn : carrier removal rate (cm-1 per particle) KN :carrier removal rate for neutron irradiation (cm-1 per neutron) Kp : carrier removal rate per proton (cm-1 per proton) KPL :photoluminescence damage factor (a.u.) k, :technology scaling factor (dimensionless) KT :pre factor in the emission rate (K2 s- 1)

Kt : lifetime damage factor ( cm2 s/particle) L : transistor length (J.lm) lc : laser diode cavity length (J.lm) L0 : extrinsic Debije length (J.lm) LE : emitter length of a bipolar transistor (J.lm) LET :linear energy transfer of ionising radiation (MeV/cm2/mg) Leff : effective channel length of a MOSFET (J.lm) Ln :electron diffusion length (em) L 0 : ligh~ output of a laser diode or a light emitting diode (a.u.) LP :hole diffusion length (em) m : particle mass (g) me :electron mass (0.91095x10-30 kg) M 2 : atomic mass (g) n :free electron or carrier density (cm-3)

n i : number of spin up electrons n1 :number of spin down electrons

XVIII List of Symbols

N :Avogadro's number (6.02204x1023 mor1)

NA :acceptor density (cm-3)

N: : surface acceptor density in a HEMT ( cm-2)

N AA : deep acceptor density ( cm-3)

Nat :Atomic density of the target material (at/cm3)

N0 :donor or doping density (cm-3)

Non : deep donor density ( cm-3)

Neff :effective doping density (cm-3)

NF : high frequency noise figure (dB) NFmin :minimum noise figure (dB) ni :intrinsic carrier concentration (cm-3)

nif : ideality factor of a junction diode (usually l:Snif:'::2) Nit : interface trap surface density ( cm-2)

Nitacceptor :acceptor-like interface trap surface density (cm-2)

Nitdonor :donor-like interface trap surface density (cm-2)

NM : noise margin of an inverter (V) NMm : high noise margin of an inverter (V) NMw : low noise margin of an inverter (V) Not : oxide trap surface density ( cm-2)

n, :electron density in the 2-DEG of a HEMT (cm-2)

N, :doping density at the surface (cm-3)

NT : trap density ( cm-3)

p : free hole density ( cm-3)

P : stopping number of the material Pa :amorphous volume generation rate (cm-3s-1)

PE : perimeter of the emitter of a bipolar transistor (f.!m) PL :light power of a LD or a LED (W/cm2)

P max : maximum solar cell power (W) Pp :point defect production parameter( ... ) q : electron charge in absolute value (1.60218x10-19 C) R : parameter describing the recombination of point defects from different

damage cascades ( cm2)

r8 : base resistance (Q) rsE : total base-emitter resistance (Q) Rchan :channel resistance of a PET (Q) RE : emitter resistance (Q) Rout :output resistance of a PET (Q) Rp : projected range of a particle (f,!m) R, : surface recombination rate (em%) Rspeak :peak surface recombination rate (cm3/s) Rso : series resistance of a PET (Q) RT :trap introduction rate (cm-1)

Rtot :total resistance of a PET (Q) s : ion implantation damage ratio S : magnetic dipole moment of the electron spin (Am-2)

List of Symbols XIX

Sd :deposited non-ionising energy (keV cm2/g) sg :surface generation velocity (cm/s) sr :surface recombination velocity (cm/s) t :time (s) T : absolute temperature (K) T0 : temperature above which no ion implantation damage is formed (K) TA :annealing temperature (K) tBo :time to breakdown of a gate oxide (s) T IRR : irradiation temperature (K) Tmax : DLTS peak maximum temperature (K) tox : oxide thickness (nm) v :particle velocity (cm/s) VA1 : part of the threshold voltage of a HEMT (V) VB : substrate voltage (V) VsE : base-emitter voltage (V) Vbi :built-in potential of a junction (V) Vel : damage cluster potential barrier (V) Vd : full depletion voltage of a radiation detector (V) Vos : drain-to-source voltage (V) VF :forward diode bias (V) VFB : flat-band voltage (V) VFD : full depletion voltage of a detector (V) V 0 : gate voltage (V) Vas : gate-to-source voltage (V) Vin : input voltage of an inverter (V) Vit : voltage related to the interface-trapped charge (V) V mg : gate voltage corresponding with the mid gap current (V) Voc : open circuit voltage of a solar cell (V) Voff : cut-off voltage of a HEMT (V) V OT : voltage related to the positive (or negative) oxide charge (V) Vout : output voltage of an inverter (V) Vp : bias during filling pulse (DLTS) (V) Vp0 : pinch-off voltage (V) VR : reverse diode bias (V) Vsat : saturation velocity of carriers (cm/s) V so : stretch-out voltage (V) VT : threshold voltage (V) vth :thermal velocity of carriers (cm/s) Vtr : transition voltage for an irradiated bipolar transistor (V) W : depletion width (J.tm) WE : emitter width of a bipolar transistor (J.tm) Weff : effective width of a MOSFET (J.tm) W1B : intrinsic base width (J.tm) Xj : junction depth (J.tm) Z, Zh ~: atomic numbers or charges

XX List of Symbols

Zw : width of a FET (Jlm)

List of Greek Symbols

a QQ

d

llbb lXc lXex Q';t

a;,t f3 f3' f3e Prk Me MIT Mg.s

11/s Me M,OL ~Qot

~ST

~vfb

~VGIDL

~Vit

: absorption coefficient (cm-1)

:model parameter threshold voltage HEMT (=2.5xl0-12 eVm413)

:model parameter saturation drain current MESFET (Y1)

:band-to-band contribution to the absorption coefficient (cm-1)

:cavity loss coefficient (cm-1)

: excitonic contribution to the absorption coefficient (cm-1)

: interface trap scattering parameter ( cm2)

:oxide trap scattering parameter (cm2)

: current gain of a bipolar transistor : model parameter saturation drain current MESFET (A v-K)

:Bohr magnetron (9.274015x10-28 J/G) : peak current gain :conduction band offset at the heterojunction of a HEMT (eV) : trap level enthalpy ( e V) :surface generation current (A) : change in base current (A) :change in collector current (A) : channel length change or reduction (!lm) :radiation-induced trapped oxide charge (C/cm2)

: trap level entropy ( e V /K) : change in flat band voltage (V) : change in the gate-induced drain leakage voltage (V) : change of the threshold voltage due to radiation-induced interface traps

(V) : change in the threshold voltage due to radiation-induced oxide-trapped

charge (V) : change in threshold voltage (V) : permittivity of GaAs (F/cm) : permittivity of silicondioxide (F/cm) :permittivity of silicon (F/cm) :particle flux (particles/cm2 s) : particle fluence (particles/cm2)

: Schottky barrier height (V) : metal workfunction (V)

XXII List of Greek Symbols

I;

17 1'/o A,

Ao AH.~IO f.l,/1{)

Jlm f.leff

f.lH f.lrnax f.1n V,V0

p Pr Pm ()"

: broadening parameter of the band-to-band part of the absorption coeffi cient

: broadening parameter of the excitonic part of the absorption coefficient :conversion efficiency solar cell(%) :slope efficiency of a laser or light emitting diode (mW/mA) : wavelength of light/photon (nm) : decay constant of plasma damage concentration profile (nm) :fitting parameter saturation drain current MESFET (Y1)

:carrier mobility (cm2Ns) :magnetic dipole moment (vector) : effective mobility (cm2Ns) : magnetic dipole moment (A m-2)

:maximum mobility (cm2Ns) :electron mobility (cm2Ns) :frequency, resonance frequency (s-1)

:resistivity (Q em) : facet reflectance : mass density of target (g/cm3)

:capture cross section (cm2)

: conductivity (Q-1 cm-1)

:capture cross section for electrons (cm2)

:capture cross section for holes (cm2)

:capture cross section of interface traps (cm2)

:lifetime of a LD or a LED (ns) :annealing time constant (s) :capture time constant (DLTS) (s) :emission time constant (DLTS) (s) : generation lifetime (s) :non-radiative recombination lifetime (s) :initial lifetime of a LD or a LED (ns) :recombination lifetime (s) : radiative recombination lifetime (s) :radial frequency (=2nv) (s-1)

: surface potential (V)