Table Of ContentGraphene for Post- Moore Silicon Optoelectronics
Graphene for Post Moore
‐
Silicon Optoelectronics
Yang Xu, Khurram Shehzad, Srikrishna Chanakya Bodepudi,
Ali Imran, and Bin Yu
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v
Contents
Preface ix
Acknowledgments xi
Biography xii
1 Graphene for Silicon Optoelectronics 1
1.1 Introduction 1
1.2 Optical Absorption 2
1.3 Emergence of Graphene in Silicon Optoelectronics 3
1.4 Photodetection in Graphene 4
1.4.1 Performance Metrics 5
1.4.2 Photovoltaic Effect 5
1.4.3 Photoemission in Graphene Schottky Junctions 6
1.4.4 Thermionic Emission in Graphene-based Interfaces 7
1.4.5 Hot Electron-based Photodetection 9
1.4.5.1 Photothermoelectric Effect (PTE) 10
1.4.5.2 Photobolometric Effect (PBE) 12
1.4.5.3 Photothermionic (PTI) Effect 13
1.4.5.4 Photogating Effect 13
1.4.6 Infrared Modulators 16
1.4.7 Photovoltaic Devices 16
1.5 Outlook 17
References 18
2 Growth and Transfer of Graphene for Silicon Optoelectronics 21
2.1 Introduction 21
2.2 Growth of Graphene 21
2.2.1 Growth Dynamics of CVD Gr and Choice of Substrate 22
2.2.2 Growth on Metallic Substrates 24
2.2.3 Direct Growth on Dielectric Substrates 26
2.2.4 Direct Growth on Semiconductor Substrates 29
2.2.5 Large- scale CVD Growth of Graphene 31
2.3 Dielectric Deposition on Graphene 33
2.4 Graphene Transfer Methods 35
vi Contents
2.5 Fabrication of Solution-p rocessed Graphene and Integration with Silicon 38
2.6 Graphene Transfer on Flexible Silicon 39
2.7 Graphene Integration with Silicon in CMOS Process 40
2.8 Challenges and Future Prospectives 41
References 42
3 Physics of Graphene/Silicon Junctions 47
3.1 Introduction 47
3.2 Physics of Schottky Junction 48
3.3 Measurement of Schottky Barrier Height 53
3.3.1 Capacitance Voltage Measurement 53
3.3.2 Current–Voltage Measurement 54
3.3.3 Photoelectric Measurement 55
3.3.4 Thermionic Emission Measurements 55
3.4 2D Materials and Schottky Junctions 58
3.5 Challenges and Future Prospective 61
References 63
4 Graphene/Silicon Junction for High-performance Photodetectors 65
4.1 Introduction 65
4.2 Ultraviolet Photodetectors 65
4.3 Visible to Near-infrared Photodetector 68
4.4 Broadband Photodetectors 71
4.5 Hybrid Gr/Si Photodetectors 75
4.6 Challenges and Perspectives 80
References 81
5 Graphene/Silicon Solar Energy Harvesting Devices 85
5.1 Introduction 85
5.2 Photovoltaic Mechanism and Performance Parameters of Graphene/
Silicon Solar Cells 86
5.3 Theoretical Efficiency Limits of Graphene Silicon Solar Cells 88
5.4 Optimization of Graphene/Silicon Solar Cells 89
5.4.1 Doping of Graphene 89
5.4.2 Light Trapping in Silicon 92
5.4.3 Antireflection Coating 94
5.4.4 Interface Engineering 97
5.4.5 Surface Passivation 100
5.5 Challenges and Perspectives 101
References 102
6 Graphene Silicon- integrated Waveguide Devices 107
6.1 Introduction 107
6.2 Hybrid Waveguide Photodetector 111
6.3 Hybrid Waveguide Modulator 114
6.3.1 Electro- optical Modulator 115
6.3.2 Thermo- optic Modulator 117
Contents vii
6.4 Challenges and Prospectives 117
References 118
7 Graphene for Silicon Image Sensor 121
7.1 Introduction 121
7.2 Quantum Dot- based Infrared Graphene Image Sensor 123
7.3 Graphene Thermopile Image Sensor 124
7.4 Graphene THz Image Sensor 125
7.5 Curved Image Sensor Array 126
7.6 Neural Network Image Sensors 127
7.7 Graphene Charge- coupled Device Image Sensor 128
7.8 Graphene- based Position- sensitive Detector 132
7.9 Challenges and Perspectives 136
References 137
8 System Integration with Graphene for Silicon Optoelectronics 141
8.1 Introduction 141
8.2 Graphene Silicon Flip Chips 142
8.3 Graphene Silicon Heterogeneous Integration 145
8.4 Graphene Silicon Monolithic Integration for Optoelectronics
Applications 147
8.5 Challenges and Prospective 150
References 152
9 Graphene for Silicon Optoelectronic Synaptic Devices 153
9.1 Introduction 153
9.2 Silicon Neurons 154
9.3 Synaptic Devices 156
9.4 Silicon Optoelectronic Synaptic Devices 157
9.5 ORAM Synaptic Devices 159
9.6 Graphene for Silicon Synaptic Devices 159
9.7 Synaptic Phototransistor 160
9.8 Broadband, Low-power Optoelectronic Synaptic Devices 163
9.9 Challenges and Prospects 164
References 167
10 Challenges and Prospects of Graphene–Silicon Optoelectronics 169
10.1 Emergence of Wafer‐scale Systems 169
10.2 Wafer‐scale Synthesis and Foundry Process 169
10.3 Scalable Transfer and Quality Metrics 171
10.4 Scaling Laws and Hot‐electron Effects 172
10.5 Optical Modulators 173
10.6 Infrared Photodetectors 174
10.7 Neuromorphic Optoelectronics 176
References 176
Index 177
ix
Preface
Miniaturization of electronic devices – a primary step that drives Moore’s law –
allows the number of digital electronic devices to roughly double by every two years
within a fixed cost and area while improving their performance and functionality.
However, such progress in power‐efficient, high‐performance, small device foot-
print, and low‐cost devices has come to a halt as further scaling down leads to dif-
ficulty in achieving complex doping profiles and excessive leakage currents. This
issue is elevated when devices are scaled down below 3 nm, where bulk semicon-
ductors lose their structural quality and show degrading charge transport and opto-
electronic properties. In this context, projecting device performance beyond the
scaling limits of Moore’s law requires technologies based on novel materials, cir-
cuits, and device architecture. Graphene and two‐dimensional (2D) materials have
emerged as alternate candidates with atomically thin structures showing excellent
charge transport properties and prototypes in computational and noncomputational
applications.
Although the domination of Si technology is unlikely to be abandoned in the fore-
seeable future, the growing benefits of graphene‐based electronics call for hybrid
device architectures that incorporate existing remarkable technological evolution
and commercial success of Si CMOS technology while adopting the novel features
of graphene. “More than Moore” or noncomputational systems, such as photodetec-
tors and modulators for image sensors, light detection and ranging (LiDAR), lasers,
biomedical sensors, and neuromorphic and radio‐frequency devices, are swiftly
advancing beyond Si electronics when integrated with graphene and other 2D mate-
rials by adapting their benefits of low‐power consumption and intrinsic scalability.
Fully integrated prototypes of 2D/Si chips, especially graphene, have been realized
for diverse applications, including image sensor arrays and optical receivers. Most
of these prototypes are developed on the integrated silicon chips where silicon
devices provide driver, source, and readout circuitry. This book discusses the basics,
applications, challenges, and opportunities regarding integrating graphene with Si
technologies, with a special emphasis on graphene–Si (Gr/Si) optoelectronic devices
in the post‐Moore era.
It might be helpful to summarize the important aspects of Gr/Si‐integrated
devices in optoelectronics in the post‐Moore era. Our book also discusses the pro-
gress and future challenges from synthesis to device fabrication and related physics
x Preface
of high‐quality, wafer‐scale Gr/Si‐integrated optoelectronic devices. All these
aspects of the Gr/Si devices are relevant to a broad research community in chemis-
try, materials science, and electronic engineering. This book is arranged to discuss
the opportunities and challenges of Gr/Si systems, where each chapter emphasizes
selected topics such as high‐performance photodetectors, energy‐harvesting devices,
and image sensors and their corresponding progress and challenges. Special empha-
sis is given to emerging applications like optoelectronic synaptic devices, optical
modulators, and infrared image sensors. This book will serve as a good reference for
graduate students, postdocs, and scientists from academia and industry.
15 July 2022 Prof. Yang Xu,
On behalf of all the authors,
Zhejiang University, Hangzhou, China
xi
Acknowledgments
We would like to thank Ms. Shaoyu Qian and their publishing team from Wiley for
their great support. We also would like to sincerely thank the significant and out-
standing contributions from our team members including Dr. Lixiang Liu,
Dr. Dajian Liu, Dr. Zhixiang Zhang, Dr. P. Pham, Dr. Jianhang Lv, Dr. Dong Pu,
Dr. K. Dianey, M. Ali, Xiaocheng Wang, Xiaoxue Cao, A. Anwar, M. Malik, and
Xinyu Liu. Without their great support and remarkable dedication, we could not
have finished this book. This book is supported by National Natural Science
Foundation of China (NSFC) (Grant Nos. 92164106, 61874094, and 62090034).
