Effects of reactor pressure and residence time on GaN MOVPE growth efficiency

Experimental and modeling study of GaN MOVPE is carried out for a single-wafer horizontal reactor with a premixed precursor injection and for the multiwafer production-scale Planetary Reactor Aix2000HT where III- and V-group precursors are injected separately. In the Planetary Reactor the growth rate is found to strongly decrease with residence time at a constant pressure and to noticeably increase with pressure for a given residence time. At the 400 mbar pressure the former effect is mainly caused by the parasitic deposit growth over the reactor ceiling, while the latter effect is due to the mass-transport redistributing the growth rate on the substrate. At the 800 mbar pressure a sublinear character of the growth rate variation with the TMGa precursor flow rate evidences for a generation of nanoparticles in the reactor chamber. In some regimes both trends counteract each other, giving a weak variation of the growth rate on the reactor pressure. In the single-wafer horizontal reactor only a quite negligible (≈10%) variation of the growth rate with pressure and residence time has been found. This indicates almost no losses in this reactor, which should result from the short residence times of the reacting mixture in the hot zone and premixed gas injection into the reactor.