The tremendous progress of crystal growth and microfabrication technologies over the last two decades has allowed us to explore a new field of semiconductor device research. The quantum mechanical wavenature of electrons, expected to appear in nanometre-scale semiconductor structures, has been used to create novel semiconductor devices. The Resonant Tunnelling Diode (RTD), which utilises the electron-wave resonance occurring in double potential barriers, emerged as a pioneering device in this field in the middle of the 1970s. The idea of resonant tunnelling (RT) was first proposed by Tsu and Esaki in 1973, shortly after Molecular Beam Epitaxy (MBE) appeared in the research field of compound semiconductor crystal growth. Since then, RT has become of great interest and has been investigated both from the standpoint of quantum transport physics and also its application in functional quantum devices. Despite its simple structure, the RTD is indeed a good laboratory for electron-wave experiments, which can investigate various manifestations of quantum transport in semiconductor nanostructures. It has played a significant role in disclosing the fundamental physics of electron-waves in semiconductors, and enables us to proceed to study more complex and advanced quantum mechanical systems.

This book is designed to describe both the theoretical and experimental aspects of this active and growing area of interest in a systematic manner, and so is suitable for postgraduate students beginning their studies or research in the fields of quantum transport physics and device engineering.