| dc.description.abstract | With the continuous increase in applications and reduction in price, light emitting diodes (LEDs) has been emerged to be one of the major semiconductor devices. Commercially, growing thin films for an LED is mainly accomplished in an MOCVD (metal organic chemical vapor deposition) chamber. Taking the GaN thin film for example, both the precursor gases of trimethyl gallium and nitrogen are introduced into the reactor through designated inlets, they then flow over a high-temperature susceptor. The high temperature induces the pyrolysis and chemical reactions of the precursor gases and the reactant of GaN is eventually deposited on the surface of wafers, which are placed on the susceptor. For growing a large area and high-quality GaN thin film, a uniformly thermal flow field on the susceptor surface is essential because this is the prerequisite for producing uniform chemical reactions. Consequently, through understandings of the reactor’s thermal flow and, furthermore, a well control of it, is critical to the low-cost and high-yield fabrication.
This study aims to develop new User Defined Functions within the framework of ANSYS-Fluent Software for simulating three-dimensional thermal and flow fields in the G2 and G3 Aixtron Planetary Reactors. Many works for analyzing the quality and growth rate of the deposited film through simulating flows of gases in a reactor chamber have been published. Part of them was specifically for planetary reactors. However, most of these calculations were performed by approximating the reacting chamber as axial symmetry in geometry and these were, in fact, two-dimensional cases. The complete temperature distributions, detailed flow patterns and velocity fields in a planetary reactor were not accessible in these works, not to mention the transient phenomena, which affect significantly the early-stage chemical reactions and the initial nucleations. In addition, the flow in a planetary reactor is intrinsically three dimensional. To avoid the complexity and time-consuming process in re-meshing at each time step, the technique of dynamic meshes, which is relatively straightforward to the planetary-motioned boundary conditions in ANSYS Fluent, is not used. Instead, the slide mesh technique is employed in this study. Through self-developed User Defined Functions, we demonstrate the present approach is able to simulate gas flows in a planetary chamber and the detailed dynamics of thermal and flow can be authentically captured. Finally, we demonstrate the dynamics of gas flows for three different operating conditions in both Axitron G2 and G3 chambers, respectively, and their corresponding local growth rates are calculated and discussed.
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