We have conducted a series of InGaN growths using a modified MOCVD horizontal reactor, namely two-heater MOCVD reactor, by varying substrate temperature, ceiling temperature and growth pressure. When the ceiling temperature is fixed at 800^oC, the measured InN growth efficiency in InGaN exhibits an activation energy of 0.97 eV for substrate temperature >650^oC, a value close to InN decomposition energy (1.2 eV), indicating the InGaN growth at high temperatures here is governed mainly by the dissociation of InN, similar to the case by conventional MOCVD. More interesting results are observed on the series of ceiling temperture samples. At a substrate temperature of 625^oC, where the decomposition of InN, if exists, is insignificant, the InN growth efficiency is observed to remain almost constant with increasing ceiling temperature and begin to drop considerably for ceiling temperature >800^oC. Such a declining in InN growth efficiency is ascribed to the parasitic reactions involved with TMIn reactants in the gas phase, as confirmed by the results of growth pressure experiment.

  Additionally, we have found that the PL properties of InGaN films strongly depend on the ceiling temperature. As the ceiling temperature is increasing from 700 to 800^oC, the peak energy of films grown at 625^oC is found to be nearly unchanged at ~1.73 eV (730 nm), however, its intensity improves remarkably, nearly by two orders of magnitude. Our results demonstrate that the use of ceiling temperature can effectively improve the luminescence efficiency of MOCVD-grown InGaN film, which may shed a light on the exploration of high quality InGaN materials emitting at long wavelengths.

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