Two dimensional hole (2DHG) and electron gases (2DEG) in wurtzite GaN/Al(x)Ga(1-x)N/GaN heterostructures are induced by piezoelectric and spontaneous polarization. The sheet carrier concentration and the electronic transport properties of the two dimensional carrier gases located close to one of the AlGaN/GaN interfaces are therefore sensitive to a high number of different physical properties such as polarity, alloy composition, strain, and barrier thickness. In this paper, the transport properties of 2DEGs and 2DHGs with sheet carrier concentrations between 2x10(12) and 10(13) cm(-2) are evaluated by a combination of C-V profiling, Hall effect and Shubnikov-de-Haas measurements. By comparison of theoretical and experimental results we demonstrate that the formation as well as the transport properties of two dimensional carrier gases in GaN/AlGaN/GaN heterostructures are dominated by polarization induced interface charges.