Transport of gas-phase species stored in stagnant volumes under a GaN metalorganic vapor phase epitaxy horizontal reactor

Three-dimensional simulations of hydrodynamics and chemical reactions have been made for GaN metalorganic vapor phase epitaxy in a horizontal two-split-flow reactor. The time-dependent behavior of gas-phase species stored in various types of stagnant volumes such as return-flows and boundary layers has been elucidated both after turn-off and after turn-on of trimethylgallium (TMG) feed. As the gas flow rate increases, the size of the return-flow and relevant stagnant volumes becomes larger, and it takes more time to carry away stored species out of the reactor space after turn-off. When there are several spatially connected stagnant volumes from the upstream to downstream direction, the draining process from each stagnant volume is not an isolated and single phenomenon but is described as a cascade and interactive phenomenon among these stagnant volumes. That is, the time constant under the exponential decay phase in a stagnant volume is influenced by diffusion-dominated phenomena in the stagnant volume existing directly before. The mass fraction of the TMG and adduct after turn-on increases rapidly with a smaller time constant compared with that in the turn-off case.