This book contains most, but regrettably not all, the papers that were presented at The Advanced Research Workshop, held July 1-5, 1997, at Smolenice Castle, Slovak Republic. The problem of angular divergence is of great importance in quantum electronics: low divergence is required not only in most of practical laser applications, but also for achieving high efficiency of parametric laser frequency conversion, and harmonic generation. The large volume of available studies aimed at improving the pump systems and the spectroscopic properties of lasing media, brought about no more than 2-3 fold increases in laser efficiency, while concurrent studies of angular divergence and the implementation of the findings, resulted in several order of magnitude of increases in radiance. The spatial beam structure that is formed in the laser cavity together with the active element constitute the most critical laser elements. The engineering devices, such as excitation systems, lasing gas circulation systems, etc., are usually at the top of the agenda of scientific meetings and of gatherings of engineering experts. The divergence problem has never been discussed by a broad community of experts in this field.

The Workshop Heterostructure Epitaxy and Devices HEAD'97 was held from October 12 to 16, 1997 at Smolenice Castle, the House of Scientists of the Slovak Academy of Sciences and was co-organized by the Institute of Electrical Engineering, Slovak Academy of Sciences, Bratislava and the Institute of Thin Film and Ion Technology, Research Centre, liilich. It was the third in a series of workshops devoted to topics related to heterostructure epitaxy and devices and the second included into the category of Advanced Research Workshops (ARW) under sponsorship of the NATO. More than 70 participants from 15 countries attended (Austria, Belarus, Belgium, Czech Republic, Finland, Germany, Greece, Hungary, Italy, Poland, Russia, Slovakia, Ukraine, the United Kingdom and the USA). Novel microelectronic and optoelectronic devices are based on semiconductor heterostructures. The goal of the ARW HEAD'97 was to discuss various questions related to the use of new materials (e.g. compound semiconductors based on high band-gap nitrides and low band-gap antimonides) and new procedures (low-temperature epitaxial growth), as well as new principles (nanostructures, quantum wires and dots, etc.) aimed at realizing high-performance heterostructure based electronic devices. Almost 70 papers (invited and contributed oral presentations as well as posters) were presented at the ARW HEAD'97 and the main part of them is included into these Proceedings.

Five questions dominated the ARW on Physics and Materials Science of High Temperature Superconductors, of which this book forms the permanent record. Briefly, these are: (i) How close are we to a unified theory? The consensus is that we are not. (ii) Flux pinning: can it be achieved in bulk materials? Still an open question. The following three questions are related. (iii) Can grain boundary contributions be brought under control? (iv) What is the real requirement for purity and general chemistry control? (v)What is the practical outlook for bulk products - tapes and wires? One of the conclusions is that the geometry and dimensions in thin films are the key parameters that facilitate the realization of high current densities and, consequently, their commercial application. On the other hand, the very large number of poorly understood microstructural, chemical and mechanical variables involved in the preparation of bulk materials are currently prohibiting large scale commercialization of wires and tapes.

From October 15 to 19, 1995 a Workshop on Hetero- structureEpitaxyandDeviceswasheldatSmoleniceCastlenear Slovakia'scapital Bratislava. The intention ofthisWorkshop was toestablishandstrengthentiesbetweenscientistsoftheformerly Socialist East and Middle-European states with their colleagues fromtheWesterncountries. WiththisaimtheWorkshopfoundthe financialsupportbyNATOwhichtremendouslyhelpedtofacilitate organizingthemeeting That the Workshop was also a scientific success is evidenced by the present volume comprising a selection of the contributed papers. We are confident that the reader of these Proceedings can convincehimselfofthe highqualityofthe work whose results are presented here. We hope that this and the numerousdiscussionsbetweenthe participants ofthe Workshop will promote cooperations among scientists from the countries representedatthemeeting. It is a pleasure to express our gratitude to NATO and, as representatives ofthe institutions involved in the organization, to Lubomir Malacky (Institute of Electrical Engineering, Slovak Academy of Sciences) and Hergo-Heinrich Wehmann (Institute for Semiconductor Technology, Technical University Braun- schweig) whose dedicated work was most essential for the Workshop. A. Schlachetzki J. Novak November1995 xiii SIMULATIONOFIII-VLAYERGROWTH y. ARIMA DepartmentofPhysics, Gakushuin University 1-5-1 Mejiro, Toshima-ku, Tokyo 171, Japan AND T. IRISAWA ComputerCenter, Gakushuin University 1-5-1 Mejiro, Toshima-ku, Tokyo 171, Japan 1. Introduction Since it was reported [1] that the intensities of RHEED for the growing surface of aGaAs crystal in the process of MBE oscillate with a period correspondingto the completion of a monolayer, this phenomenon has been applied to the thin layer growth of man-made superlattices.

Five questions dominated the ARW on Physics and Materials Science of High Temperature Superconductors, of which this book forms the permanent record. Briefly, these are: (i) How close are we to a unified theory? The consensus is that we are not. (ii) Flux pinning: can it be achieved in bulk materials? Still an open question. The following three questions are related. (iii) Can grain boundary contributions be brought under control? (iv) What is the real requirement for purity and general chemistry control? (v)What is the practical outlook for bulk products - tapes and wires? One of the conclusions is that the geometry and dimensions in thin films are the key parameters that facilitate the realization of high current densities and, consequently, their commercial application. On the other hand, the very large number of poorly understood microstructural, chemical and mechanical variables involved in the preparation of bulk materials are currently prohibiting large scale commercialization of wires and tapes.

This book contains most, but regrettably not all, the papers that were presented at The Advanced Research Workshop, held July 1-5, 1997, at Smolenice Castle, Slovak Republic. The problem of angular divergence is of great importance in quantum electronics: low divergence is required not only in most of practical laser applications, but also for achieving high efficiency of parametric laser frequency conversion, and harmonic generation. The large volume of available studies aimed at improving the pump systems and the spectroscopic properties of lasing media, brought about no more than 2-3 fold increases in laser efficiency, while concurrent studies of angular divergence and the implementation of the findings, resulted in several order of magnitude of increases in radiance. The spatial beam structure that is formed in the laser cavity together with the active element constitute the most critical laser elements. The engineering devices, such as excitation systems, lasing gas circulation systems, etc., are usually at the top of the agenda of scientific meetings and of gatherings of engineering experts. The divergence problem has never been discussed by a broad community of experts in this field.

The Workshop Heterostructure Epitaxy and Devices HEAD'97 was held from October 12 to 16, 1997 at Smolenice Castle, the House of Scientists of the Slovak Academy of Sciences and was co-organized by the Institute of Electrical Engineering, Slovak Academy of Sciences, Bratislava and the Institute of Thin Film and Ion Technology, Research Centre, liilich. It was the third in a series of workshops devoted to topics related to heterostructure epitaxy and devices and the second included into the category of Advanced Research Workshops (ARW) under sponsorship of the NATO. More than 70 participants from 15 countries attended (Austria, Belarus, Belgium, Czech Republic, Finland, Germany, Greece, Hungary, Italy, Poland, Russia, Slovakia, Ukraine, the United Kingdom and the USA). Novel microelectronic and optoelectronic devices are based on semiconductor heterostructures. The goal of the ARW HEAD'97 was to discuss various questions related to the use of new materials (e.g. compound semiconductors based on high band-gap nitrides and low band-gap antimonides) and new procedures (low-temperature epitaxial growth), as well as new principles (nanostructures, quantum wires and dots, etc.) aimed at realizing high-performance heterostructure based electronic devices. Almost 70 papers (invited and contributed oral presentations as well as posters) were presented at the ARW HEAD'97 and the main part of them is included into these Proceedings.

Dieser Buchtitel ist Teil des Digitalisierungsprojekts Springer Book Archives mit Publikationen, die seit den Anfangen des Verlags von 1842 erschienen sind. Der Verlag stellt mit diesem Archiv Quellen fur die historische wie auch die disziplingeschichtliche Forschung zur Verfugung, die jeweils im historischen Kontext betrachtet werden mussen. Dieser Titel erschien in der Zeit vor 1945 und wird daher in seiner zeittypischen politisch-ideologischen Ausrichtung vom Verlag nicht beworben.