A numerical study of the effect of pulse duration on preventing particle generation during the AlN pulsed MOCVD process

A numerical model is built to understand the transport phenomenon during the pulsed MOCVD process. The relations between the transport behavior of the precursors and the pulse duration for III, V, and pure H₂ pulses are studied. The results show that the mass fraction of precursors in the chamber during the III or V pulses becomes stable if they are longer in duration than a certain value. The duration of the pure H₂ pulse has a greater effect on particle generation than the duration of the III or V pulse. On the other hand, the V pulses can easily overtake the III pulses before reaching the substrate because of the lower Pe number of the NH₃. Using an III/V ratio of 1 results in more AlN particles in the high-temperature region during the H₂ pulse after the III pulse. By extending the duration of the H₂ pulse which follows the III pulse, there is a significant reduction in the generation of particles per cycle. When the duration of the H₂ pulse after the III pulse is increased to a certain time, the amount of particles generated after the III pulse becomes equal to that generated after the V pulse. When an even lower particle generation is required, the duration of H₂ pulses after the III and V pulses should be extended at the same time.