Atomic Layer Epitaxy, Softcover reprint of the original 1st ed. 1990

This book provides a detailed study of the Atomic Layer Epitaxy technique (ALE), its development, current and potential applications. The rapid development of coating technologies over the last 25 years has been instrumental in generating interest and expertise in thin films of materials, and indeed the market for thin film coatings is currently £3 billion with projected annual growth of 20 to 30% [1]. ALE is typical of thin-film processes in that problems in the processing or preparation of good quality epitaxial films have been overcome, resulting in better performance, novel applications of previously unsuitable materials, and the development of new devices. Many materials exhibit interesting and novel properties when prepared as thin films and doped. Vapour-deposited coatings and films are used extensively in the semiconductor and related industries for making single devices, integrated circuits, microwave hybrid integrated circuits, compact discs, solar reflective glazing, fibre optics, photo voltaic cells, sensors, displays, and many other products in general, everyday use. The ALE technique was developed by a research team led by Tuomo Suntola, working for Instrumentarium Oy in Finland. The key members of this team were lorma Antson, Arto Pakkala and Sven Lindfors. In 1977, the research team moved from Instrumentarium to Lohja Corporation, where they continued the development of ALE and were granted a patent in the same year. By 1980, the technique was sufficiently advanced that they were producing flat-screen electroluminescent displays based on a manganese-doped zinc sulphide layer.

1 Chemical aspects of the Atomic Layer Epitaxy (ALE) process.- 1.1 Introduction.- 1.2 Requirements for ALE growth.- 1.3 Source materials used in ALE.- 1.3.1 Elements.- 1.3.2 Inorganic compounds.- 1.3.2.1 Use of halides to grow metal chalcogenide films.- 1.3.2.2 Preparation of oxides.- 1.3.2.3 Preparation of nitrides.- 1.3.2.4 Preparation of GaAs and other III-V compounds.- 1.3.3 Complexes containing organic ligands.- 1.3.3.1 Preparation of sulphides.- 1.3.3.2 Preparation of oxides.- 1.3.4 Organometallics.- 1.4 Doping of thin films.- 1.5 Growth of thin films.- 1.5.1 Factors affecting the growth rate.- 1.5.2 Factors affecting the quality of the films.- 1.6 Concluding remarks and outlook 36.- References.- 2 Theoretical aspects of ALE growth mechanisms.- 2.1 Introduction.- 2.2 Theoretical methods.- 2.2.1 Quantum chemical methods.- 2.2.2 Surface modelling techniques.- 2.3 ALE systems.- 2.3.1 II-VI compounds.- 2.3.1.1 ZnS.- 2.3.1.2 ZnSe, ZnTe, CdTe.- 2.3.2 III-V compounds.- 2.3.2.1 ALE.- 2.3.2.2 Mechanisms of other epitaxial growth techniques.- 2.3.3 Silicon 56.- 2.3.3.1 Theoretical surface studies.- 2.3.4 Other systems.- 2.4 Conclusions 60.- References.- 3 Comparison of ALE with other techniques.- 3.1 Inroduction.- 3.1.1 Materials.- 3.1.2 Substrate preparation.- 3.2 MOVPE.- 3.1.1 Method of growth.- 3.2.2 Starting materials for MOVPE.- 3.2.2.1 Alkyls.- 3.2.2.2 Hydrides.- 3.2.2.3 Adducts.- 3.2.3 Gas handling equipment.- 3.2.4 Reactor cell design.- 3.2.4.1 Hydrodynamics.- 3.2.4.2 Boundary layer phenomenon.- 3.2.4.3 Streamlines.- 3.2.4.4 Turbulent and laminar flow.- 3.2.4.5 The effect of heat.- 3.2.4.6 Reactant gas mixing.- 3.2.4.7 Cell inlet area expansion.- 3.2.4.8 Temperature gradients above the susceptor.- 3.2.4.9 Boundary layers above the susceptor.- 3.2.4.10 Current cell designs.- 3.2.4.11 Vertical cell.- 3.2.4.12 Vertical chimney reactor.- 3.2.4.13 The upside-down reactor.- 3.2.4.14 The trumpet inlet cell.- 3.2.4.15 Criteria for good cell design.- 3.2.5 Mechanism of growth.- 3.3 Molecular beam epitaxy.- 3.3.1 Method of growth.- 3.3.2 Starting materials.- 3.3.3 Equipment.- 3.3.3.1 The UHV system.- 3.3.3.2 The substrate holder.- 3.3.3.3 Knudsen cells.- 3.3.3.4 Shutters.- 3.3.4 Analytical equipment.- 3.3.4.1 Mass spectrometry.- 3.3.4.2 RHEED.- 3.3.4.3 Auger.- 3.3.5 Mechanism of growth.- 3.3.5.1 Matrix elements.- 3.3.5.2 Doping elements.- 3.4 Hybrid areas.- 3.4.1 Low pressure MOVPE.- 3.4.2 Vacuum chemical epitaxy.- 3.4.3 Chemical beam epitaxy.- 3.4.4 MOMBE.- 3.4.5 Gas source MBE.- 3.5 Comparison of MOVPE, MBE and ALE.- 3.5.1 Discussion.- References.- 4 ALE of III-V compounds HO.- 4.1 Introduction.- 4.2 Self-limiting mechanism.- 4.3 Experimental approaches for ALE of III-V compounds.- 4.3.1 MOVPE.- 4.3.2 Hydride VPE.- 4.3.3 MOMBE.- 4.3.4 Laser-assisted ALE.- 4.3.5 Pseudo-ALE techniques.- 4.3.5.1 Modulation enhanced epitaxy (MEE).- 4.3.5.2 Flow rate modulation epitaxy (FME).- 4.4 Review of experimental results.- 4.4.1 Thickness uniformity.- 4.4.2 Electrical properties.- 4.4.3 Intentional doping of material grown by ALE.- 4.4.4 Selective epitaxy.- 4.4.5 Quantum well heterostructures.- 4.4.6 Lasers.- 4.4.7 Superalloys.- 4.4.8 Atomic-plane doping field effect transistor.- 4.5 Potential applications of ALE.- 4.6 Conclusion 152.- References.- 5 ALE of II-VI compounds.- 5.1 Introduction.- 5.2 ALE.- 5.2.1 Principle of ALE.- 5.2.2 ALE growth system.- 5.2.3 Growth procedure.- 5.3 Reflection high energy electron diffraction (RHEED) observation.- 5.3.1 Growth process.- 5.3.1.1 Growth process on (001) GaAs substrate.- 5.3.1.2 Initial growth process on (001) Zn chalcogenide layers.- 5.3.1.3 Low-temperature growth.- 5.3.2 Adsorption process.- 5.3.2.1 RHEED intensity variations with time.- 5.3.2.2 Adsorption time.- 5.3.3 Desorption process.- 5.4 Characterisation of ALE-grown Zn chalcogenide layers.- 5.4.1 Surface morphology.- 5.4.2 X-ray characterisation of lattice strain.- 5.4.3 Photoluminescence properties.- 5.5 Summary 177.- References.