N. Balkan – författare

Since the arrival of the transistor in 1947, research in hot electrons, like any field in semiconductor research, has grown at a stunning rate. From a physicist's point of view the understanding of hot electrons and their interactions with the lattice has always been a challenging problem of condensed matter physics. Recently, with the advent of novel fabrication techniques such as electron beam or plasma etching and the advanced growth techniques such as the molecular beam epitaxy (MBE) and metallo-organic chemical vapour deposition (MOCVD), it has become possible to fabricate semiconductor devices with sub-micron dimensions where the electrons are confined to two (quantum well), one (quantum wire) or zero (quantum dot) dimensions. In devices of such dimensions a few volts applied to the device result in the setting up of very high electric fields, hence a substantial heating of electrons. Thus electronic transport in the device becomes non- linear and can no longer be described using the simple equations of Ohm's law. The understanding of the operations of such devices, and the realisations of more advanced ones make it necessary to understand the dynamics of hot electrons. There is an obvious lack of good reference books on hot electrons in semiconductors. The few that exist either cover a very narrow field or are becoming quite outdated. This book is therefore written with the aim of filling the vacuum in an area where there is much demand for a comprehensive reference book. The book is intended for both established researchers and graduate students, and gives a complete account of the historical development of the subject, together with current research interests and future trends. The contributions are written by leading scientists in the field. They cover the physics of hot electrons in bulk and low dimensional device technology. The material is organised into subject area that can be classified broadly into five groups: (1)introduction and overview, (2)hot electron phonon interactions and the ultra-fast phenomena in bulk and two dimensional structures, (3)hot electrons in both long and short quantum wires and quantum dots, (4) hot electron tunnelling and hot electron transport in superlattices, and (5) novel devices based on hot electron transport. The chapters are grouped according to subject matter as far as possible. However, although there is much overlap of ideas and concepts, each chapter is essentially independent of the others.

Instabilities associated with hot electrons in semiconductors have been investigated from the beginning of transistor physics in the 194Os. The study of NDR and impact ionization in bulk material led to devices like the Gunn diode and the avalanche-photo-diode. In layered semiconductors domain formation in HEMTs can lead to excess gate leakage and to excess noise. The studies of hot electron transport parallel to the layers in heterostructures, single and multiple, have shown abundant evidence of electrical instability and there has been no shortage of suggestions concerning novel NDR mechanisms, such as real space transfer, scattering induced NDR, inter-sub band transfer, percolation effects etc. Real space transfer has been exploited in negative-resistance PETs (NERFETs) and in the charge-injection transistor (CHINT) and in light emitting logic devices, but far too little is known and understood about other NDR mechanisms with which quantum well material appears to be particularly well-endowed, for these to be similarly exploited. The aim of this book is therefore to collate what is known and what is not known about NDR instabilities, and to identify promising approaches and techniques which will increase our understanding of the origin of these instabilities which have been observed during the last decade of investigations into high-field longitudinal transport in layered semiconductors. The book covers the fundamental properties of hot carrier transport and the associated instabilities and light emission in 2-dimensional semiconductors dealing with both theory and experiment.