In this work secondary ion mass spectroscopy was used to investigate the incorporation of oxygen, carbon, and hydrogen impurities in smooth N-face (0 0 0 1) and Ga-face (0 0 0 1) GaN films grown by metalorganic chemical vapor deposition. The smooth N-face films were obtained on vicinal sapphire substrates, of which the misorientations 2 degrees, 4 degrees, and 5 degrees towards [10 (1) over bar0]Al2O3, as well as 4 degrees and 5 degrees towards [11 (2) over bar0]Al2O3 were explored. Results are presented for variations in temperature, pressure, V/III ratio, and Ga flow. Additionally, the incorporation of intentional dopants Si, for n-type doping, and Mg, for p-type doping were investigated. The misorientation angle and direction did not impact the impurity incorporation on the N-face. In comparison to the Ga-face, the N-face GaN films contained significantly higher concentrations of oxygen, however, demonstrated lower levels of carbon. Incorporation of Mg and Si dopants were found to be similar in N-face and Ga-face films. Additionally, significantly sharper Mg-doping profiles in N-face films in comparison to Ga-face films were observed. (C) 2008 Elsevier B.V. All rights reserved.