Cryst. Res. Technol. 38, No. 3 – 5, 237 – 249 (2003) / DOI 10.1002/crat.200310028 2003 © 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 0232-1300/03/3-504-0237 $ 17.50+.50/0 Advances in modeling of wide-bandgap bulk crystal growth M. V. Bogdanov 1 , S. E. Demina 1 , S. Yu. Karpov 1 , A. V. Kulik 1 , M. S. Ramm* 2 , Yu. N. Makarov 3 1 Soft-Impact, Ltd. P.O. Box 33, 27 Engels av., St. Petersburg, 194156 Russia 2 Ioffe Physical-Technical Institute, RAS, St. Petersburg, 194021 Russia 3 Semiconductor Technology Research, Inc., P.O. Box 70604, Richmond, VA 23255, USA Received 13 October 2002, accepted 25 November 2002 Published online 15 April 2003 Key words sublimation growth, SiC, AlN, heat and mass transfer, dislocations, porous media. PACS 81.10.Aj, 81.10.-h, 81.10.Hk, 02.60.Pn, 81.05.Rm, 72.80.Ey We review key aspects of sublimation growth of wide-bandgap semiconductors like SiC, AlN and GaN, and show how modeling can help to solve a number of practical problems. As the temperature distribution in the growth chamber is the most critical factor in the sublimation technology, we discuss in detail specific features of heat transfer with the focus on the porous materials normally involved in the growth system: powder source, thermal insulation, and graphite. The species transport is simulated using advanced models accounting for a multicomponent vapor and the kinetics of chemical interaction of nitrogen-containing species with the surface of group-III nitrides. The effect of growth conditions on parasitic phase formation is analyzed. To optimize the growth system design and operating conditions, we suggest an inverse-problem approach instead of commonly used trial-and-error methods. This simulation procedure has proved quite efficient for getting design solutions, which could hardly be found by conventional straightforward methods. In particular, we demonstrate the effectiveness of the inverse modeling for finding the growth conditions, which provide crystals of desired shapes. A special analysis is made to establish a correlation between the growth conditions and defect distribution in the grown crystal, with the focus on thermoelastic stress produced by temperature gradients. The high-temperature dynamics of gliding dislocations and consequent plastic stress relaxation in the material is examined. The prospective of global modeling of wide-bandgap crystal growth by sublimation and still open questions are discussed. 1 Introduction Wide-bandgap semiconductors, such as SiC and Group-III nitrides, are advanced materials widely used in high-power, high-frequency, high-temperature electronics and optoelectronics. The breakthrough in their applications in the middle of the 1990s was associated with the development of blue/green light emitting diodes and lasers [1], high-power high electron mobility transistors [2], and the first commercially available high-voltage Schottky diodes [ 3]. However, further progress in the wide-bandgap semiconductor technology is primarily hindered by the lack of homoepitaxial substrates suitable for the epitaxy of multi-layered high-quality device structures. To date, SiC substrates with a mean dislocation density of about 10 4 -10 5 cm -2 and a micropipe density of less than about 10 2 cm -2 are commonly available, which is still insufficient for commercial applications in high-power electronics. Further reduction in the dislocation density and complete elimination of micropipes is strongly desirable for SiC wafers. Due to their specific properties, AlN and GaN are considered as the best substrate materials for nitride-based microelectronics and optoelectronics, respectively. It was only recently that the growth of AlN crystals of 10×15 mm 2 AlN crystals at a rate of ~ 0.9 mm/h suitable for the production was reported [ 4], while the GaN growth technology did not yet go beyond the laboratory practice. Nevertheless, the development of AlN and GaN growth technology is carrying out intensively over the world. ____________________ * Corresponding author: e-mail: ramm@softimpact.ru