Complex studies of intentional GaN carbon doping from propane during MOVPE were performed in a wide range of growth conditions. A strong dependence of carbon doping efficiency on growth rate and ammonia flow is revealed, while dependence of carbon doping efficiency on reactor pressure is small. Atomic force microscopy confirms the good quality of the GaN:C layers for doping levels as high as 2*10(19) cm(-3) grown with growth rate up to 45 mu m/h. The dependence of carbon incorporation into GaN is proportional to the propane concentration to the power 3/2 in most growth regimes, but for very high growth rate a linear or sub-linear component of the dependence becomes prominent. (C) 2016 Elsevier B.V. All rights reserved.