Nanophononics thermal generation, transport, and conversion at the nanoscaleedited by Zlatan Aksamija

"Heat in most semiconductor materials, including the traditional group IV elements (Si, Ge, diamond), III-V compounds (GaAs, wide-bandgap GaN), and carbon allotropes (graphene, CNTs), as well as emerging new materials like transition metal dichalcogenides (TMDCs), is stored and transported by lattice vibrations (phonons). Phonon generation through interactions with electrons (in nanoelectronics, power, and nonequilibrium devices) and light (optoelectronics) is the central mechanism of heat dissipation in nanoelectronics. This book focuses on the area of thermal effects in nanostructures, including the generation, transport, and conversion of heat at the nanoscale level. Phonon transport, including thermal conductivity in nanostructured materials, as well as numerical simulation methods, such as phonon Monte Carlo, Green's functions, and first principles methods, feature prominently in the book, which comprises four main themes: (i) phonon generation/heat dissipation, (i) nanoscale phonon transport, (iii) applications/devices (including thermoelectrics), and (iv) emerging materials (graphene/2D). The book also covers recent advances in nanophononics--the study of phonons at the nanoscale. Applications of nanophononics focus on thermoelectric (TE) and tandem TE/photovoltaic energy conversion. The applications are augmented by a chapter on heat dissipation and self-heating in nanoelectronic devices. The book concludes with a chapter on thermal transport in nanoscale graphene ribbons, covering recent advances in phonon transport in 2D materials. The book will be an excellent reference for researchers and graduate students of nanoelectronics, device engineering, nanoscale heat transfer, and thermoelectric energy conversion. The book could also be a basis for a graduate special topics course in the field of nanoscale heat and energy."--Provided by publisher Cover 1 Half Title 2 Title Page 4 Copyright Page 5 Table of Contents 6 Preface 10 1: Modeling Self-Heating Effects in Nanoscale Devices 12 1.1 Introduction 12 1.2 Self-Heating 14 1.2.1 General Considerations 14 1.2.2 Arizona State University Model Description 19 1.3 Simulation Results 22 1.3.1 Self-Heating Effects in FD-SOI Devices 22 1.3.1.1 Basic findings 22 1.3.1.2 Thermal boundary conditions and proper choice of the device simulation domain 24 1.3.2 Can We Reduce Self-Heating? 26 1.3.2.1 Single-gate versus dual-gate FD-SOI devices 26 1.3.2.2 FD-SOI devices with diamond and AlN BOX 28 1.3.3 Multiscale Modeling: Modeling of Circuits (CS and CD Configuration) 31 1.4 Conclusions and Future Directions of Research 37 2: Simulation of Charge and Thermal Transport 42 2.1 Introduction 42 2.2 The Boltzmann Transport Equation for Electrons 43 2.3 Electron Scattering Rates 44 2.4 The Phonon Boltzmann Transport Equation 47 2.5 Phonon Scattering and Anharmonic Decay 48 3: Phonon Emission and Absorption Spectra in Silicon 52 3.1 Introduction 52 3.2 The Adiabatic Bond Charge Model for Phonons 53 3.3 Numerical Computation of Phonon Spectra 56 3.4 Results and Discussion 64 3.5 Conclusions 68 4: Device Simulation, Including the Full Phonon Dispersion 74 4.1 Introduction 74 4.2 Monte Carlo Device Simulation 75 4.3 Thermal Properties of Silicon 80 4.4 Results 86 4.5 Conclusions 94 5: Anharmonic Decay of Nonequilibrium Intervalley Phonons in Silicon 98 5.1 Introduction 98 5.2 Intervalley Phonon Emission 100 5.3 Monte Carlo Simulation of Anharmonic Phonon Decay 103 5.4 Scattering of Acoustic Phonons 105 5.5 Results and Discussion 107 6: Phonon Monte Carlo: Generating Random Variates for Thermal Transport Simulation 120 6.1 Introduction 120 6.2 Generating Random Variates 122 6.2.1 The Inversion Method 122 6.2.2 The Rejection Method 123 6.3 Overview of Phonon Monte Carlo 125 6.4 Generating Phonon Attributes in PMC 130 6.4.1 Thermal Phonons with Full Dispersion in 2D 130 6.4.2 Thermal Phonons with an Isotropic Dispersion in 3D 134 6.5 Diffuse Boundary Scattering 135 6.6 Contacts 139 6.6.1 3D Internal Contacts 140 6.6.2 3D Boundary Contacts 141 6.6.3 2D Contacts 142 6.7 Energy Conservation 143 6.8 Conclusion 145 7: Hybrid Photovoltaic-Thermoelectric Solar Cells: State of the Art and Challenges 150 7.1 Introduction 150 7.2 A Primer on Thermoelectricity 152 7.3 Strategies of Thermoelectric Solar Energy Conversion 154 7.3.1 Solar Thermoelectric Generators 155 7.3.2 Hybrid Cogenerative Solar Thermoelectric Generators 155 7.3.3 Hybrid Thermoelectric-Photovoltaic Generators 156 7.4 Photovoltaic Generation 157 7.4.1 Physical Principles 158 7.4.2 The p-n Junction 162 7.4.3 Single-Junction Solar Cells: Diode under Illumination 164 7.4.4 Photovoltaic Technology 168 7.4.5 PV Efficiency, Energy Gap, and Temperature 169 7.5 Thermoelectric Hybridization of PV Cells 175 7.5.1 Conditions for Enhanced Efficiency in HTEPV Devices 178 7.5.2 Optimal Layout of the Thermoelectric Stage 181 7.5.3 Optical and Thermal Concentration 183 7.6 Summary and Concluding Remarks 185 8: Phonon Transport Effects in Ultranarrow, Edge-Roughened Graphene Nanoribbons 194 8.1 Introduction 195 8.2 Methods 198 8.2.1 Phonon Dispersion 198 8.2.2 Phonon Dispersion Features 201 8.2.3 Phonon Transport within NEGF 203 8.3 Influence of Roughness on Phonon Transport 204 8.3.1 Influence of Roughness on Phonon Transmission 204 8.3.2 Influence of Roughness on Different Phonon Modes 207 8.3.3 Ballistic, Diffusive, and Localized Phonon Modes 208 8.4 Transmission Effects in Width-Modulated GNRs 210 8.4.1 Influence of Width Modulation on Acoustic Modes 211 8.4.2 Influence of Width Modulation on Optical Modes 211 8.4.3 Influence of Width Modulation on Low-Density-Mode Regions 212 8.4.4 Influence of Width Modulation on Quasi-Acoustic Modes 212 8.4.5 General Discussion of Width-Modulated Features 214 8.5 Thermal Conductance 215 8.6 Characteristic Scattering Length Scales 217 8.6.1 Mean Free Path for Scattering 217 8.6.2 Localization Length 220 8.7 Thermal Conductivity 222 8.8 Conclusions 224 Index 234 Annotation Heat in most semiconductor materials, including the traditional group IV elements (Si, Ge, diamond), III-V compounds (GaAs, wide-bandgap GaN), and carbon allotropes (graphene, CNTs), as well as emerging new materials like transition metal dichalcogenides (TMDCs), is stored and transported by lattice vibrations (phonons). Phonon generation through interactions with electrons (in nanoelectronics, power, and nonequilibrium devices) and light (optoelectronics) is the central mechanism of heat dissipation in nanoelectronics. This book focuses on the area of thermal effects in nanostructures, including the generation, transport, and conversion of heat at the nanoscale level. Phonon transport, including thermal conductivity in nanostructured materials, as well as numerical simulation methods, such as phonon Monte Carlo, Green's functions, and first principles methods, feature prominently in the book