Metalorganic vapor phase epitaxy (MOVPE) of GaN was performed using hydrogen (H 2 ), nitrogen (N 2 ) and H 2 /N 2 mixtures thereof as the carrier gas in the high temperature buffer growth range. The effect of carrier gas on the structural and morphological characteristics of the epilayers was systematically studied using interference and atomic force microscopy (AFM), photoluminescence (PL) measurements at 2 K, Raman spectroscopy and X-ray diffraction (XRD). The higher the N 2 content in the carrier gas, the more pinholes are observed, the lower compressive strain and the higher dislocation density in the layers. A carrier gas composition range was defined at which GaN layers with acceptable structural and morphological characteristics are achieved.

MOVPE growth of GaN/sapphire was studied with respect to growth control by using in situ reflectometry. The main requirements for reproducible growth were identified to be the control of the substrate temperature and the avoidance of parasitic deposition. This is accomplished by using emissivity corrected pyrometry to monitor the growth temperature and modeling to find flow parameters which lead to strongly reduced parasitic deposition.

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