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-spli t-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 trimethylgalli um (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 car ry away stored species out of the reactor space after turn-off. When there are several spatially connected stagnant volumes from the upstream to downs tream direction, the draining process from each stagnant volume is not an i solated 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 m ass fraction of the TMG and adduct after turn-on increases rapidly with a s maller time constant compared with that in the turn-off case.