Molecular Beam Epitaxy

From Research to Mass Production

Mohamed Henini

• Publisher: Elsevier
• Year: 2018
• eBook ISBN: 9780128121375
• Edition: 2
• Topic: Physical Sciences
• Subtopic: Condensed Matter

Molecular Beam Epitaxy (MBE): From Research to Mass Production, Second Edition, provides a comprehensive overview of the latest MBE research and applications in epitaxial growth, along with a detailed discussion and 'how to' on processing molecular or atomic beams that occur on the surface of a heated crystalline substrate in a vacuum. The techniques addressed in the book can be deployed wherever precise thin-film devices with enhanced and unique properties for computing, optics or photonics are required. It includes new semiconductor materials, new device structures that are commercially available, and many that are at the advanced research stage.This second edition covers the advances made by MBE, both in research and in the mass production of electronic and optoelectronic devices. Enhancements include new chapters on MBE growth of 2D materials, Si-Ge materials, AIN and GaN materials, and hybrid ferromagnet and semiconductor structures.- Condenses the fundamental science of MBE into a modern reference, speeding up literature review- Discusses new materials, novel applications and new device structures, grounding current commercial applications with modern understanding in industry and research- Includes coverage of MBE as mass production epitaxial technology and how it enhances processing efficiency and throughput for the semiconductor industry and nanostructured semiconductor materials research community

Chapter 1

Molecular Beam Epitaxy of Transition Metal Monopnictides

Gavin R. Bell, The University of Warwick, Coventry, United Kingdom

Abstract

The chapter reviews MBE growth of transition metal monopnictide materials, MX (M=Mn, Ni, Cr, etc. and X=P, As, Sb, Bi). The first section outlines the basic crystal structures and lattice parameters. Then MBE growth of common MX materials on different substrates is tabulated along with a more in-depth discussion of the nearly-lattice-matched NiSb(0001)/GaAs(111). Sections 1.3 and 1.4 outline magnetic and electronic properties respectively, including surface effects. Sections 1.5 and 1.6 cover MnAs and MnSb in more detail, including the magneto-structural transition in MnAs and surface reconstructions in both materials. Polymorphism is discussed, particularly in relation to half-metallic ferromagnetic zincblende structure phases, before a summary and outlook is given covering outstanding questions and possible avenues for fruitful research in the future.

Keywords

Molecular beam epitaxy; spintronics; ferromagnetism; MnAs; MnSb; semiconductor; transition metal monopnictide

1.1 Introduction

The transition metal monopnictides comprise equal atomic concentrations of a metal element M (often Mn, Ni or Cr) and a group 15 (pnictogen) element X. It is possible to mix both metal elements (e.g., Mn_1–yFe_yAs (de Campos et al., 2006) or Cr_1–yMn_ySb (Dankelmann, 1994)) and pnictogen elements (e.g., MnAs_1–xSb_x (Dankelmann, 1994), (Uchitomi et al., 2004)). Deliberate deviation from 1:1 M:X stoichiometry is also possible, e.g., by increasing the transition metal content (Morikawa and Wada, 2004). However, such alloyed and off-stoichiometric MX materials have mostly been grown as bulk crystals or polycrystals rather than as thin films by MBE. This chapter will deal with binary stoichiometric compounds only, particularly the Mn monopnictides.

There has been a great deal of interest in thin-film epitaxial MX materials because of their varied magnetic and magneto-optical properties (Motizuki et al., 2010; Rache Salles et al., 2009; Saparov et al., 2012). Much of this work has been motivated by potential applications in spintronics and magneto-electronics (Samarth et al., 2003; Hirohata et al., 2015). Functions include magneto-optic isolators (Amemiya et al., 2008), magnetic tunnel junctions (Takahashi and Tanaka, 2000; Sugahara and Tanaka, 2002), lateral spin valves (Holub et al., 2007), magneto-resistive switching, spin-field effect transistors (Islam and Akabori, 2017), spin-light emitting diodes (Hanna et al., 2011), magneto-caloric effect (MCE) for room-temperature magnetic refrigeration, magneto-logic (Pampuch et al., 2003), and magneto-optics and spin injection layers for quantum dot or quantum well lasers (Bhattacharya et al., 2009). For such applications, the epitaxial compatibility of transition metal monopnictides MX materials with conventional semiconductor materials, particularly the III–V materials, is advantageous. High quality epitaxy allows control over film orientation and strain, as well as the growth of more complex structures, such as magnetic multilayers (Uchitomi et al., 2004) and superlattices (Torikai et al., 1993). Recently there has been interest in pressure-induced superconductivity in MX materials (Chong et al., 2016) starting with its discovery in MnP (Cheng et al., 2015). Biaxial stress due to epitaxial growth on a mismatched substrate could conceivably act in a similar way. The richness of the magnetic and magneto-structural phase behavior of MX materials offers both a test-bed for basic physics (e.g., in MnP, pure Lifshitz-type critical behavior (Paduan-Filho and Becerra, 2003)) and the opportunity to engineer phenomena through the structural and compositional precision offered by MBE (e.g., the MCE via structurally-driven metamagnetism (de Campos et al., 2006; Gercsi and Sandeman, 2010)). Further control could be achieved through the deliberate growth of MX materials in metastable polymorphs. In particular, half-metallic ferromagnetic (HMF) materials possess full spin polarization of conduction electrons: the Fermi level straddles a band gap for one spin orientation only, while the other spin exhibits metallic behavior. This makes HMF materials very attractive for spintronic applications. Several metastable MX polymorphs are predicted to be robust HMF materials.

The crystal structures of the transition metal monopnictides are usually hexagonal or orthorhombic. These are, respectively, the B8₁ NiAs structure (space group P6₃/mmc) and B31 MnP structure (Pnma), a distortion of the B8₁ structure. However, a good deal of modelling and experimental work has been devoted to cubic polymorphs of the MX materials, specifically the B3 zincblende structure (F$\overline{4}$

3m). Many cubic B3-structure transition metal monopnictides are predicted to be strong HMF materials; this property is also predicted for several MX materials in the B4 wurtzite structure (P6₃mc) (Xie et al., 2003). The four crystal structures are illustrated in Fig. 1.1. The nearest-neighbour coordination is different between the NiAs/MnP structures and the zincblende/wurtzite structures. While zincblende and wurtzite structures have tetrahedrally coordinated atoms (four M atoms surround each X atom and vice versa), local bonding in the B8₁ structure is different between M and X atoms. The structure can be thought of as alterna...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of Contributors
• Chapter 1. Molecular Beam Epitaxy of Transition Metal Monopnictides
• Chapter 2. Migration-enhanced Epitaxy for Low-dimensional Structures
• Chapter 3. Molecular Beam Epitaxy of High Mobility Silicon, Silicon Germanium and Germanium Quantum Well Heterostructures
• Chapter 4. Molecular Beam Epitaxy Growth of SiGeSn Alloys
• Chapter 5. Molecular Beam Epitaxy of Dilute Nitride Optoelectronic Devices
• Chapter 6. Nonpolar Cubic III-nitrides: From the Basics of Growth to Device Applications
• Chapter 7. Molecular Beam Epitaxy of Al(Ga)N Nanowire Heterostructures and Their Application in Ultraviolet Optoelectronics
• Chapter 8. Kinetics of Metal-Rich PA Molecular Beam Epitaxy of AlGaN Heterostructures for Mid-UV Photonics
• Chapter 9. InAsBi Materials
• Chapter 10. Molecular Beam Epitaxy of GaAsBi and Related Quaternary Alloys
• Chapter 11. Molecular Beam Epitaxy of IV–VI Semiconductors: Fundamentals, Low-dimensional Structures, and Device Applications
• Chapter 12. Site-Controlled Epitaxy of InAs Quantum Dots on Nanoimprint Lithography Patterns
• Chapter 13. Droplet Epitaxy of Nanostructures
• Chapter 14. Layer-by-Layer Growth of Thin Films of Ternary Alloys of II–VI Semiconductors by Submonolayer Pulsed Beam Epitaxy (SPBE)
• Chapter 15. Molecular Beam Epitaxy-Grown Wide Band Gap II–VI Semiconductors for Intersubband Device Applications
• Chapter 16. Zinc Oxide Materials and Devices Grown by Molecular Beam Epitaxy
• Chapter 17. Epitaxial Systems Combining Oxides and Semiconductors
• Chapter 18. Nanoscale Engineering of Ge-based Diluted Magnetic Semiconductors for Room-Temperature Spintronics Application
• Chapter 19. Molecular Beam Epitaxy of Hybrid Topological Insulator/Ferromagnetic Heterostructures and Devices
• Chapter 20. Challenges and Opportunities in Molecular Beam Epitaxy Growth of 2D Crystals: An Overview
• Chapter 21. Molecular Beam Epitaxy of Graphene and Hexagonal Boron Nitride
• Chapter 22. Molecular Beam Epitaxy of Transition Metal Dichalcogenides
• Chapter 23. Growth and Characterization of Fullerene/GaAs Interfaces and C60-Doped GaAs and AlGaAs Layers
• Chapter 24. Thin Films of Organic Molecules: Interfaces and Epitaxial Growth
• Chapter 25. Molecular Beam Epitaxy of Wide Gap II−VI Laser Heterostructures
• Chapter 26. THz Quantum Cascade Lasers
• Chapter 27. GaSb Lasers Grown on Silicon Substrate for Telecom Applications
• Chapter 28. GaP/Si-Based Photovoltaic Devices Grown by Molecular Beam Epitaxy
• Chapter 29. Systems and Technology for Production-Scale Molecular Beam Epitaxy
• Chapter 30. Mass Production of Optoelectronic Devices
• Chapter 31. Mass Production of Sensors Grown by Molecular Beam Epitaxy
• Chapter 32. Molecular Beam Epitaxy as a Mass Production Enabling Technology for Electronic/Optoelectronic Devices
• Chapter 33. Molecular Beam Epitaxy in the Ultravacuum of Space: Present and Near Future
• Index