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Gallium nitride (GaN) is a III-V semiconductor that is used in many optoelectronic and electronic devices including LEDs, lasers and transistors. Its optical and electrical properties can be widely varied by adding other elements into the crystal structure. Previously reported research has attributed observations of yellow luminescence and high resistivity to intentionally and unintentionally carbon doped GaN (GaN:C). The exact role of carbon is not completely resolved, partly because the formation of different carbon related defects depends on growth conditions. Here, intentionally doped GaN:C grown by nitrogen rich ammonia Molecular Beam Epitaxy (NH3-MBE) using carbon tetrabromide (CBr4) as the carbon doping source was investigated. The amount of carbon incorporation was coarsely regulated by growth temperature. Surface roughness of samples with different growth temperatures and ammonia fluxes were imaged with Atomic Force Microscopy. With decreasing temperature, the roughness increased until at 650 °C the surface became smoother indicating a possible change of the growth mode. Electrical properties were analyzed by Hall Effect and Circular Transmission Line Model measurements. We examine whether an increasing carbon concentration leads to an increased resistivity due to carbon defects. The results will show whether nitrogen rich growth conditions are suitable for producing resistant carbon doped GaN layers.