Über die Autorin bzw. den Autor

Hans J. Scheel started the Scheel Consulting company in 2001 after retiring from the Swiss Federal Institute of Technology. Starting out with a chemical background, he has more than 40 years of experience with crystal growth and epitaxy in university as well as industry. For his achievements in bulk crystal growth and epitaxy technologies, he received awards from IBM and from Swiss, British, Korean Crystal Growth Associations, was elected member of the Russian Academy of Engineering Sciences, and received his D.Sc. from Tohoku University, Japan. He is co-author and editor of 6 books, author of more than 100 publications and patents, has organized international workshops on crystal technology and has been visiting professor at Osaka and Tohoku Universities, Japan, as well as Shandong University, China.

Tsuguo Fukuda is the editor of Crystal Growth Technology, published by Wiley.

Von der hinteren Coverseite

This volume deals with the technologies of crystal fabrication, of crystal machining, and of epilayer production and is the first book on industrial and scientific aspects of crystal and layer production. Highest-quality crystals and epitaxical layers form the base for many of industries technological advances, including telecommunication, computer and electric energy technology, and those technologies based on lasers and nonlinear-optic crystals. Furthermore, automobile electronics, audiovisual equipment and infrared night-vision all depend on high-quality crystals and epilayers, as do novel technologies currently in development and planned for the future.

This book contains 29 contributions of leading crystal technologists covering the following topics:
* General aspects of crystal growth technology
* Silicon
* Compound semiconductors
* Oxides and halides
* Crystal machining
* Epitaxy and layer deposition

Scientific and technological problems of production and machining of industrial crystals are discussed by top experts, most of the m from the major growth industries and crystal growth centres.

It is anticipated that this volume will serve all scientists and engineers involved in crystal and epilayer fabrication. In addition, it will be useful for the users of crystals, for teachers and graduate students in materials sciences, in electronic and other functional materials, chemical and metallurgical engineering, micro-and optoelectronics including nanotechnology, mechanical engineering and precision-machining, microtechnology, and in solid-state sciences. Also consultants and specialists will profit from this book, as will those interested in crystals, epilayers, and their production for saving energy (GaN- and SiC-based high-power electronics and light-emitting diodes for illumination) and for renewable energy sources (economic high-efficiency solar cells and forthcoming laser-fusion energy).

Aus dem Klappentext

This volume deals with the technologies of crystal fabrication, of crystal machining, and of epilayer production and is the first book on industrial and scientific aspects of crystal and layer production. Highest-quality crystals and epitaxical layers form the base for many of industries technological advances, including telecommunication, computer and electric energy technology, and those technologies based on lasers and nonlinear-optic crystals. Furthermore, automobile electronics, audiovisual equipment and infrared night-vision all depend on high-quality crystals and epilayers, as do novel technologies currently in development and planned for the future.

This book contains 29 contributions of leading crystal technologists covering the following topics:
* General aspects of crystal growth technology
* Silicon
* Compound semiconductors
* Oxides and halides
* Crystal machining
* Epitaxy and layer deposition

Scientific and technological problems of production and machining of industrial crystals are discussed by top experts, most of the m from the major growth industries and crystal growth centres.

It is anticipated that this volume will serve all scientists and engineers involved in crystal and epilayer fabrication. In addition, it will be useful for the users of crystals, for teachers and graduate students in materials sciences, in electronic and other functional materials, chemical and metallurgical engineering, micro-and optoelectronics including nanotechnology, mechanical engineering and precision-machining, microtechnology, and in solid-state sciences. Also consultants and specialists will profit from this book, as will those interested in crystals, epilayers, and their production for saving energy (GaN- and SiC-based high-power electronics and light-emitting diodes for illumination) and for renewable energy sources (economic high-efficiency solar cells and forthcoming laser-fusion energy).

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Crystal Growth Technology

John Wiley & Sons

Chapter One

HANS J. SCHEEL SCHEEL CONSULTING, CH-8808 Pfaeffikon SZ, Switzerland

ABSTRACT

The industrial production of crystals started with A. Verneuil with his flamefusion growth method 1902. He can be regarded as the father of crystal growth technology as his principles of nucleation control and crystal-diameter control are adapted in most later growth methods from the melt, like Tammann, Stvber, Bridgman, Czochralski, Kyropoulos, Stockbarger, etc. The important crystal pulling from melts named after Czochralski was effectively developed by Teal, Little and Dash.

The multi-disciplinary nature of technology of crystal and epilayer fabrication, the complex multi-parameter processes - where ten or more growth parameters have to be compromised and optimized, and also the scaling problem have impeded the scientific development of this important area. Only recently has the numerical simulation of Czochralski melts started to become useful for growth technologists, the deep understanding of the striation problem allowed the experimental conditions to grow striation-free crystals to be established, and the control of epitaxial growth modes permitted the preparation of atomically flat surfaces and interfaces of importance for the performance of opto-electronic and superconducting devices.

Despite the scale of the multi-billion dollar crystal and epilayer fabrication and crystal-machining industry and the annual need worldwide of at least 400 engineers, there is so far no formation of specialists for crystal production, epitaxy technology, crystal machining and surface preparation. A special curriculum is required due to the multi-disciplinary character of crystal-growth technology (CGT) which does not fit into a single classical university discipline like chemical, mechanical, materials, or electrical engineering, or crystallography, thermodynamics, solid-state physics, and surface physics. The education scheme for CGT has to include all these disciplines and basic sciences to such an extent that the finished engineers and scientists are capable of interacting and collaborating with specialists from the various disciplines. It is up to the interested industries to request CGT engineers from the technical universities and engineering schools.

Crystal-growth technology and epitaxy technology had developed along with the technological development in the 20th century. On the other hand, the rapid advances in microelectronics, in communication technologies, in medical instrumentation, in energy and space technology were only possible after the remarkable progress in fabrication of large, rather perfect crystals and of large-diameter epitaxial layers (epilayers). Further progress in CGT and education of CGT engineers is required for significant contributions to the energy crisis. High-efficiency white light-emitting diodes for energy-saving illumination and photovoltaic/thermo-photovoltaic devices for transforming solar and other radiation energy into electric power with high yield depend on significant advances in crystal growth and epitaxy technology. Also, the dream of laserfusion energy and other novel technologies can only be realized after appropriate progress in the technology of crystal and epilayer fabrication.

1.1 HISTORICAL INTRODUCTION

Fundamental aspects of crystal growth had been derived from early crystallization experiments in the 18th and the 19th century (Elwell and Scheel 1975, Scheel 1993). Theoretical understanding started with the development of thermodynamics in the late 19th century (Gibbs, Arrhenius, Van't Hoff) and with the development of nucleation and crystal growth theories and the increasing understanding of the role of transport phenomena in the 20th century. The phenomena of undercooling and supersaturation and the heat of crystallization were already recognized in the 18th century by Fahrenheit and by Lowitz. The corresponding metastable region, the existence range of undercooled melts and solutions, was measured and defined in 1893/1897 by Ostwald and in 1906 by Miers, whereas the effect of friction on the width of this Ostwald-Miers region was described in 1911 and 1913 by Young. Although the impact of stirring on this metastable region is important in mass crystallization of salt, sugar and many chemicals, it is not yet theoretically understood.

The rates of nucleation and crystallization in glasses were the foundation to nucleation theories. The crystal surface with steps and kinks of Kossel in 1927 allowed Stranski and Kaishew in 1934 to define the work of separation of crystal units as repeatable steps as the basis of the first crystal-growth theories. With the understanding of facet formation as a function of the entropy of fusion in 1958 by Jackson, and depending on the density of bonds in the crystal structure 1955 by Hartman and Perdok, the role of screw dislocations as continuous step sources in the formation of growth hillocks (Frank 1949), and with the generalized crystal growth theory of Burton, Cabrera and Frank 1951, many growth phenomena could be explained.

In the growth of crystals from a fluid medium (melt, solution, gas phase) the heat and mass transport phenomena also play a significant role, as was observed early by Rouelle 1745 and Frankenheim 1835. The diffusion boundary layer defined by Noyes and Whitney 1897 was used in the growth-rate equation of Nernst 1904 and confirmed by interferometric measurements of concentration profiles around growing crystals by Berg 1938 and by others. Forced convection was recognized to be beneficial for diffusion-limited growth by Wulff 1886, Kr|ger and Finke 1910, and Johnsen 1915 for open systems with stirrers, whereas smooth stirring in sealed containers can be achieved with the accelerated crucible rotation technique ACRT of Scheel 1971/1972. The growth of inclusion-free crystals from the melt can be accomplished by observing the principles of "diffusional undercooling" of Ivantsov 1951 and "constitutional supercooling" of Tiller et al. 1953. Formation of inclusions, i.e. growth instability, can be prevented in growth from solutions by sufficient flow against or along the crystal facets: Carlson 1958 developed an empirical theory which was utilized by Scheel and Elwell 1972 to derive the maximum stable growth rate and optimized programming of supersaturation for obtaining large inclusion-free crystals.

Microscopic and macroscopic inhomogeneities in doped crystals and in solid solutions are caused by segregation phenomena, which are related to mass and heat transfer. Based on the derivation of effective distribution coefficients for melt growth by Burton et al. (1953) and by van Erk (1982) for growth from solutions, the theoretical and experimental conditions for growth of striation-free crystals could be established (Rytz and Scheel 1982, Scheel and Sommerauer 1983, Scheel and Swendsen 2001).

There have been remarkable developments with respect to size and perfection of crystals, with silicon, sapphire, alkali and earth alkali halides reaching diameters up to 0.5m and weights of nearly 500 kg. These advances in Czochralski, Kyropoulos, heat-exchanger method, and Bridgman-Stockbarger growth were accompanied by numerical simulations which have become increasingly powerful to predict the optimized conditions. However, further advances in computer modelling and in the reliability of the used physico-chemical...