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Virtual Reactor: 2D Software Tool for Modeling of SiC and AlN Bulk Crystal Growth by Sublimation Method

Soft-Impact develops physical and chemical models for several software products designed by STR, Inc. The software tool Virtual Reactor, designed by STR for modeling of SiC and AlN bulk crystal growth by sublimation technique, employs advanced models of surface kinetics developed in Soft-Impact.

Experimental optimization of the growth process takes normally much effort and is time-consuming. Thus, modeling of sublimation growth can be quite beneficial if the simulation tool can predict important features of the process. The software tool Virtual Reactor provides growers with exhaustive information about numerous physical processes responsible for the growth of bulk crystal and its quality. This includes information on the final size and quality of the grown crystal, as well as the distribution of temperature, heat fluxes and other parameters in the overall reactor and along all boundaries of reactor parts at any stage of the growth, including crystal shape and powder evolution and dislocation dynamics. This, in turn, provides wide possibilities for profound investigations of the phenomena underlying the growth, allowing optimization of the reactor geometry and technology process.

The problem is considered in 2D axisymmetric approximation that provides an adequate simulation of the sublimation growth of AlN and hexagonal SiC polytypes on (0001) face. The simulation of long-term crystal growth is carried out by a series of coupled quasi-steady-state steps of the overall process. On completion of each stage, the crystal and powder shape evolution is predicted from the growth rate obtained. According to the settings predefined by the user, the heater power can be varied and the crucible or inductor coil can be shifted automatically. Then geometry of the growth system is updated along with the regeneration of the computational grid.

The growth simulation at every stage includes modeling of the heat transfer in the growth system and reactive species mass transport in the crucible. The software employs an original heterogeneous chemistry model that provides an efficient description of interaction of multi-component vapor with the reactive surface. The approach suggested allows description of the chemical processes at the gas-solid interfaces in a wide range of temperature and pressure. Virtual Reactor predicts evolution of the crystal shape and changes in the powder source parameters, porosity and mean granule size, with time.