Advances in modeling of wide‐bandgap bulk crystal growth

Abstract

. 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.

Development of 2" AlN Substrates Using SiC Seeds

“…Balkas et al (Balkas et al, 1997)). The duration of growth process is limited by the degradation of the crucible (de Almeida & Wang et al, 2006) and of the graphite insulation (Cai et al, 2006) as well as by continuous operation of the source that requires the temperature gradients within the source to be as low as possible (Bogdanov et al, 2003;. The growth temperature influence the size of AlN nuclei (Yazdi et al, 2006) and thus the crystal morphology (Sitar et al, 2004).…”

“…The growth temperature influence the size of AlN nuclei (Yazdi et al, 2006) and thus the crystal morphology (Sitar et al, 2004). The dislocations in the crystal can arise both during growth or after the growth in the course of the thermomechanical stress relaxation (Bogdanov et al, 2003;Klapper, 2010;Kochuguev et al, 2001;Zhmakin et al, 2000). The effect of substrate misorientation and buffer layers on growth modes and defects in AlN sublimed onto 6H-SiC substrates were studied in Refs.…”

“…Since the AlN sublimation growth is implemented in a tightly closed crucible under high-temperature, it is difficult to study and control the growth process in situ, thus the importance of the mathematical modelling is evident (Bogdanov et al, 2003;Chen et al, 2008;de Almeida & Rojo, 2002;Ern & Guermond, 2004;Wellmann et al, 2006;Wu et al, 2005;Zhmakin, 2004). The aims of numerical simulation are to explain and to predict the growth behaviour.…”

“…Secondly, some parts of the facility could be modelled as the porous medium. Powder source is used in a number of techniques such as the metal flux method for growth of bulk GaN crystals from Li-Ga-N liquid phase (Song et al, 2004), the ammonothermal method for GaN (Yoshikawa et al, 2004), the sublimation growth of single crystals of wide bandgap semiconductors (SiC, AlN) (Bogdanov et al, 2003;Dhanaraj et al, 2003). The granular or fibrous medium is often used for the insulation.…”

Three‐dimensional thermoelastic stresses in off‐axis oriented single crystals with hexagonal symmetry

“…For a better understanding of the growth process a large number of numerical investigations has been performed, especially concerning SiC growth occuring at very high temperatures of up to 2500 K. A review of these results is given in Ref. [4]. For kinetical reasons, GaN and SiC single crystals are grown in most cases on seeds wich have a certain off-axis orientation.…”