400 BOOK Chapter 2 dealing with the semiconductordiode starts with the idealized cases of small current density and no recombination. The carrier de...

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Chapter 2 dealing with the semiconductordiode starts with the idealized cases of small current density and no recombination. The carrier density versus field expressions for a depletion layer are derived, the carrier concentrations in the different regions of the junction are represented, and the diffusion-model is finally used to derive the WAGNER-SCHOTTKY diode characteristics. As the book emphasizes the engineering point of view the reader finds here already a representative scheme of the diode and a clear definition of the diffusion-capacity in distinction to the barrier layer capacity. The complete scheme of a p-n junction at small current densities and corresponding R-C network representations are outlined. The next subchapter (2.2) is a thorough discussion of deviations from the simple diffusion model of a p-n junction. It is mentioned that especially the silicon case shows deviations due to recombination and microplasma breakdown effects. The case of high current densities is outlined in reference to the work of HERLET on abrupt symmetrical p-n junctions and an original approach of GUGGENB~‘HL for the nonsymmetrical diode is derived. The result is of practical value since most diodes are nonsymmetric. The calculated results for the potential distribution and the voltage distribution between barrier layer and spreading resistance with increasing current density are in good agreement with measured values. In the case of very high (degenerate) doping (rl 9 n,rt) the diode behavior is governed by tunneling processes. This case is dealt with in the next chapter. The authors first derive carefully the quantum mechanical problem of barrier penetration with the three solutions of Schrodinger’s equation and the corresponding amplitude functions. This solution is then applied to real degenerate junctions in the way first described by ESAKI, such that the tunnel characteristic is a superposition of currents resulting from transitions from the valence to the conduction band and vice versa. Now the p-n junction in the reverse bias case is considered. The different phenomena are discussed, as Zener- and avalanche-breakdown. The favorably low temperature dependence of this portion of the characteristics and its importance for the circuit designer are emphasized. Micro-


plasma breakdown effects and attendant increase in noise power and recombination light are described as typical for silicon and dominated by the midband dislocation levels. Thermal breakdown effects (Ge) are discussed and the important ,t-i--?~ and p-s-n diodes are mentioned. With this the authors enter into the more practical part of their book and a description of ohmic contacts, contact materials and properties of special diode types follows. Selenium and cuprous oxide diodes arc discussed. A short chapter on photodiodes and solar batteries concludes this part. Finally the important question of the temperature behavior of the diode characteristics is brought up with measured curves of the reverse current dependence on temperature for germanium and silicon diodes. The rest of the book deals with the more engineering-type questions of thermal stability, cooling problems, optimal design, circuit design and behavior in circuits, as well as de\-ice yield and aging. As this short description tells, the material presented in this book is of great concern for the electronics engineer and can bc highly- recommended to all those who desire a thorough but condensed description of this major field of device A second volr~rne is physics and technology. announced dealing with the transistor.

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INURINGthe last decade, the theoretical intcrprctation of the phenomenon of superconductivity in microscopic terms has developed remark&Iv rapidly, and now provides a large measure tit’ understanding of fundamental effects. Concurrently, an increasing awareness of the possibilities of practical exploitation has resulted in the production of such devices as superconducting magnets and switching elements for computers. At the present time, there is, therefore, some incentive for the non-specialist to seek acquaintance with the fundamentals of superconductivity, and a compact



book which presents these fundamentals clearly, and with the minimum of mathematical elaboration, might be considered widely acceptable. Professor LYNTON’S monograph does just this, and is ideal for the non-specialist, as well as providing an admirable introduction for the graduate about to embark on research or technical development. Concisely written, eminently readable, and requiring scarcely any equipment beyond that of an Honours Physics course, the text covers in the space of about 150 pages most of the essential material of experimental and theoretical significance and constitutes a succinct account of the field of superconductivity as it stands at present. The first seven chapters are devoted to an exposition of the basic concepts and phenomenological treatments, including the PIPPARD nonlocal theory. Further chapters, preparing the way for the microscopic theory, are concerned with the isotope effect, thermal conductivity and the investigation of the energy gap through the specific heat, nuclear spin relaxation, tunnelling, and transmission at sub-millimetre wavelengths. Semiconductor physicists, in particular, will appreciate the problem of an absorption edge occurring at

BOOKS THE following books may or may not be reviewed more fully at a later date. The short summary of their contents is that of the Editor,

frequencies of the order of 1011-101s sec.-l The significance of recent experimental work is well brought out and the numerous diagrams are helpful. The BARDEEN-COOPER-SCHRIEFFER theory is outlined in the eleventh chapter, and here the salient features of the treatment are emphasized, so that the nature of the derivation of essential results, e.g. the ground state energy, is readily discernible. The principle experimental implications of the BCS theory are considered, including a brief reference to ultrasonic attenuation. Other theoretical approaches, such as that of BOGOLIUBOV, are not referred to. The remaining two chapters contain short accounts of superconducting alloys and compounds, and superconducting devices. An extensive list of over 300 references is appended. It is good to see Superconductivity included in the list of Methuen Monographs, and the present volume should be welcomed by a wide variety of solid-state physicists. B. DONOVAN West$eld College, London

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