Physics of Quantum Electron Devices

The ability to engineer the bandstructure and the wavefunction over length scales previously inaccessible to technology using artificially structured materials and nanolithography has led to a new class of electron semiconductor devices whose operation is controlled by quantum effects. These structures not only represent exciting tools for investigating new quantum phenomena in semiconductors, but also offer exciting opportunities for applications. This book gives the first comprehensive treatment of the physics of quantum electron devices. This interdisciplinary field, at the junction between material science, physics and technology, has witnessed an explosive growth in recent years. This volume presents a detailed coverage of the physics of the underlying phenomena, and their device and circuit applications, together with fabrication and growth technology.

1. Introduction.- 1.1 A Perspective on the Evolution of Quantum Semiconductor Devices.- 1.2 Outline of the Book.- References.- 2. The Nature of Molecular Beam Epitaxy and Consequences for Quantum Microstructures.- 2.1 Dimensional Confinement and Device Concepts.- 2.2 Molecular Beam Epitaxy.- 2.2.1 Conceptual Picture.- 2.2.2 Reflection High Energy Electron Diffraction.- 2.2.3 Formation of Interfaces and Growth Interruption.- 2.3 The Surface Kinetic Processes and Computer Simulations of Growth.- 2.3.1 The CDRI Model.- 2.3.2 Growth Front Morphology.- 2.3.3 The CDRI Model and the Nature of GaAs/AlxGa1?xAs (100) Interfaces.- 2.4 Quantum Wells: Growth and Photoluminescence.- 2.5 Concluding Remarks.- 2.6 Recent Advances.- References.- 3. Nanolithography for Ultra-Small Structure Fabrication.- 3.1 Overview.- 3.2 Resolution Limits of Lithographic Processes.- 3.2.1 Lithography.- 3.2.2 Resolution Limits of Lithographic Methods.- 3.2.3 Photolithography and X-Ray Lithography.- 3.2.4 Ion Beams.- 3.2.5 Electron Beams.- 3.3 Pattern Transfer.- References.- 4. Theory of Resonant Tunnelling and Surface Superlattices.- 4.1 Tunnelling Probabilities.- 4.1.1 Single Barrier.- 4.1.2 Resonant Tunnelling Rates.- 4.2 Tunnelling Time.- 4.3 Pseudo-Device Calculations.- 4.3.1 The Wigner Function.- 4.3.2 Diode Response.- 4.4 Lateral Superlattices.- 4.4.1 Transport Effects.- 4.4.2 Bloch Oscillators.- 4.4.3 High Frequency Response.- References.- 5. The Investigation of Single and Double Barrier (Resonant Tunnelling) Heterostructures Using High Magnetic Fields.- 5.1 Background.- 5.2 LO Phonon Structure in the I(V) and C(V) Curves of Reverse-Biased Heterostructures.- 5.2.1 n-GaAs/(AlGa)As/GaAs Heterostructures.- 5.2.2 n-(InGa)As/InP/(InGa)As Heterostructures.- 5.2.3 Magnetocapacitance and Magnetic Freeze-out.- 5.3 Magnetotunnelling from the 2D Electron Gas in Accumulated (InGa)As/InP Structures Grown by MBE and MOCVD.- 5.4 Observation of Magnetoquantized Interface States by Electron Tunnelling in Single-Barrier n? (InGa)As/InP/n+ (InGa)As Heterostructures.- 5.5 Box Quantised States.- 5.6 Double Barrier Resonant Tunnelling Devices.- 5.6.1 Hybrid Magneto-electric States in Resonant Tunnelling Structures.- 5.6.2 Intrinsic Bistability in Resonant Tunnelling Devices.- 5.6.3 Magnetic Field Studies of Elastic Scattering and Optic Phonon Emission in Resonant Tunnelling Devices.- References.- 6. Microwave and Millimeter-Wave Resonant-Tunnelling Devices.- 6.1 Speed of Response.- 6.2 Resonant-Tunnelling Oscillators.- 6.3 Self-Oscillating Mixers.- 6.4 Resistive Multipliers.- 6.5 Variable Absolute Negative Conductance.- 6.6 Persistent Photoconductivity and a Resonant-Tunnelling Transistor.- 6.7 A Look at Resonant-Tunnelling Theory.- 6.7.1 Stationary-State Calculation.- 6.7.2 Temporal Behavior.- 6.7.3 Scattering.- 6.8 Concluding Remarks.- Note Added in Proof.- List of Symbols.- References.- 7. Resonant Tunnelling and Superlattice Devices: Physics and Circuits.- 7.1 Resonant Tunnelling Through Double Barriers and Superlattices.- 7.1.1 The Origin of Negative Differential Resistance.- 7.1.2 Coherent (Fabry—Perot-Type) Resonant Tunnelling.- 7.1.3 The Role of Scattering: Sequential Resonant Tunnelling Through Double Barriers and Superlattices.- 7.1.4 Ga0.47In0.53As/Al0.48In0.52As Resonant Tunnelling Diodes.- 7.1.5 Resonant Tunnelling Through Parabolic Quantum Wells.- 7.1.6 Resonant Tunnelling Electron Spectroscopy.- 7.2 Application of Resonant Tunnelling: Transistors and Circuits.- 7.2.1 Integration of Resonant Tunnelling Diodes and Their Circuit Applications.- a) Horizontal Integration of RT Diodes.- b) Vertical Integration of RT Diodes.- 7.2.2 Resonant Tunnelling Bipolar Transistors.- a) Circuit Applications of RTBTs.- b) Resonant Tunnelling Bipolar Transistors Operating at Room Temperature.- c) Alternative Designs of RTBTs.- d) RTBT with Multiple Peak Characteristics.- 7.2.3 Resonant Tunnelling Unipolar Transistors.- a) Resonant Tunnelling Gate Field Effect Transistor.- b) Quantum Wire Transistor.- c) The Gated Quantum Well Resonant Tunnelling Transistor.- References.- 8. Resonant-Tunnelling Hot Electron Transistors (RHET).- 8.1 RHET Operation.- 8.2 RHET Technology Using GaAs/AlGaAs Heterostructures.- 8.3 InGaAs-Based Material Evaluation.- 8.4 RHET Technology Using InGaAs-Based Materials.- 8.5 Theoretical Analyses of RHET Performance.- 8.6 Summary.- References.- 9. Ballistic Electron Transport in Hot Electron Transistors.- 9.1 Ballistic Transport.- 9.1.1 The Search for Ballistic Transport.- 9.1.2 Properties of GaAs.- 9.2 Hot Electron Transistors.- 9.2.1 Principles of Operation.- 9.2.2 Some History.- 9.3 Hot Electron Injectors.- 9.3.1 What is a Hot Electron Injector?.- 9.3.2 The Thermionic Injector.- 9.3.3 The Tunnel Injector.- 9.4 Energy Spectroscopy.- 9.4.1 Spectroscopy Defined.- 9.4.2 Band Pass Spectrometer.- 9.4.3 High Pass Spectrometer.- 9.4.4 Energy Resolution of the Square Type Barrier.- 9.4.5 Observation of Quasi Ballistic and Ballistic Electron Transport in GaAs.- 9.4.6 Observation of Ballistic Hole Transport in GaAs.- 9.5 Electron Coherent Effects in the THETA Device.- 9.5.1 Size Quantization Effects.- 9.5.2 Classical and Self-Consistent Well Potential.- 9.5.3 Tunnelling into a Well.- 9.5.4 Nonparabolicity Effects, Real and Resonant States.- 9.5.5 Interference Effects of Ballistic Holes.- 9.6 Transfer to the L Satellite Valleys.- 9.6.1 Spectroscopic Observations.- 9.6.2 Verification of the Intervalley Transfer.- 9.7 The THETA as a Practical Device.- 9.7.1 Gain Considerations.- 9.7.2 Speed Considerations.- 9.7.3 Final Comments.- References.- 10. Quantum Interference Devices.- 10.1 Background.- 10.2 Two-Port Quantum Devices.- 10.2.1 Conductance Formula.- 10.2.2 Quantum Interference Transistor.- 10.3 Multiport Quantum Devices.- 10.3.1 Conductance Formula.- 10.3.2 Quantum Reflection Transistor.- 10.3.3 Quantum Networks.- Appendix: Aharonov — Bohm Phase-shift in an Electric or Magnetic Field.- References.- Additional References.- 11. Carrier Confinement to One and Zero Degrees of Freedom.- 11.1 Experimental Methods.- 11.2 Discussion of Experimental Results.- 11.3 Conclusions.- References.- 12. Quantum Effects in Quasi-One-Dimensional MOSFETs.- 12.1 Background.- 12.2 MOSFET Length Scales.- 12.3 Special MOSFET Geometries.- 12.4 Strictly 1D Transport.- 12.4.1 Localization and Resonant Tunnelling.- 12.4.2 Hopping Transport.- 12.5 Multichannel Transport (Particle in a Box?).- 12.6 Averaged Quantum Diffusion.- 12.6.1 Weak Localization.- 12.6.2 Electron-Electron Interactions.- 12.7 Mesoscopic Quantum Diffusion (Universal Conductance Fluctuations).- 12.7.1 Universal Conductance Fluctuations at Scale Lø.- 12.7.2 Self-Averaging of Conductance Fluctuations at Larger Probe Spacings.- 12.7.3 Nonlocal Response of Conductance Fluctuations at Shorter Probe Spacings.- 12.7.4 Comprehensive Comparison Between Theory and Experiment.- 12.7.5 Internal Asymmetries of Mesoscopic Devices.- 12.8 Effect of One Scatterer.- 12.8.1 Interface Traps.- 12.8.2 Quantum Effect of One Scatterer.- 12.9 Conclusion.- References.