Virtual Reactor - Software for Modeling of Long-Term Growth of Bulk Crystals

Fig. 1. Modeling of SiC growth. Unstructured Mesh and temperature distribution in the growth system

Virtual Reactor is a family of two-dimensional software tools designed for the simulation of long-term growth of bulk crystals from the vapor phase. It allows the user to analyze the growth-related phenomena, follow the crystal shape evolution during the whole growth, study the source evolution and defect dynamics. Virtual Reactor is designed to serve for simplifying and accelerating optimization of both growth system design and process conditions and is intended to be exploited by the growth engineers for R&D and production.

Virtual Reactor is supplied as one of the following editions:

• Physical Vapor Transport editions
  - For growth of SiC crystals: VR-PVT SiC
  - For growth of AlN crystals: VR-PVT AlN
  
• Chemical Vapor Deposition edition
  - For growth of SiC crystals: VR-CVD SiC
  
• Hydride Vapor Phase Epitaxy edition
  - For growth of GaN crystals: HEpiGaNS
  (Hydride Epitaxial GaN Simulator)

Fig. 2. Specification of the growth system in GUI

Virtual Reactor provides comprehensive 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 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.

Fig. 3. Assigning the material properties in GUI

The problem is considered in axisymmetric or plane 2D approximation. 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 shape evolution is predicted from the growth rate obtained. According to the settings predefined by the user, the heater power, pressure and precursor flow rate can be varied, the reactor units or inductor coil can be shifted automatically. Then geometry of the growth system is updated along with the regeneration of the computational grid.

Fig. 4. Editing the materials database

The growth simulation at every stage includes modeling of the heat transfer, gas mixture flow and reactive species mass transport, in particular, multi-component diffusion and chemical reactions in the gas domain. The software employs a homogeneous chemistry model involving precursor decomposition and an original heterogeneous chemistry model. The approach suggested allows description of the chemical processes at the gas-solid interfaces in a wide range of temperature and pressure.

The Virtual Reactor is designed with a friendly user interface (GUI) which is aimed at minimization of the user efforts needed for the problem specification. The user needs to prescribe only the initial conditions and a set of the time moments with the desired operating conditions if they change in time. All other changes in the system configuration during the growth simulation are made automatically.

Fig. 5. Built-in visualization of the obtained results

Unstructured triangular and quadrilateral non-matched computational grids are used in numerical simulation. The grid generation is carried out for each geometry block providing the required grid density.

Run-time and post-processing visualization is available within the GUI, presenting the two-dimensional and one-dimensional distributions of temperature and other variables. In addition, the computational results are stored in files allowing a post-processing analysis using commercial Tecplot graphical package.