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History of MBE

John Orton and I have recently published a book entitled Molecular Beam Epitaxy – A Short History [1]. In that book we were not able to cover all aspects of this topic, so many significant contributions had to be omitted. In this short chapter, even more work of importance will be missing and what follows is my personal view of how molecular beam epitaxy (MBE) evolved. Before starting to describe how it occurred, we have of course to decide what we mean by MBE. As far as I can discover, the term was first used in the Proceedings of the Third International Symposium on GaAs and Related Compounds by Cho et al. [2] in order to distinguish MBE from the earlier growth methods, namely liquid phase epitaxy (LPE) and vapour phase epitaxy (VPE). So, what is MBE? One may consider it to be a refined form of vacuum evaporation, but it is clearly significantly different from simple evaporation in many ways. It usually involves multiple sources and deposition onto a heated substrate. It usually takes place in ultra-high vacuum (UHV) equipment, in order to reduce the arrival rate of unwanted species. In general, collision-free molecular beams are used to supply the required species to the substrate. It differs from many other growth methods in having many different in-situ measurements (e.g. electron diffraction or mass spectrometry), which enables the process to be controlled at an atomic level. My personal view is that there are at least two MBE topics of equal importance, there is the study of the MBE process itself and the application of MBE to provide samples and devices of the highest possible quality. In my career I have been involved in both aspects for a variety of material systems and regard them as equally significant. In this chapter I will try to summarise what went into our book and will begin by discussing the development of the MBE process before turning to its application. Before starting on this task, I recommend to the