Ga-doped ZnO (GZO) thin films with high thermal stability and high carrier mobility are essential to develop transparent conductive electrodes (TCEs). In this study, the carrier concentration and the electrical resistivity of GZO thin films are related to the Ga flow rates. GZO thin films have been grown on c-plane sapphire substrates with Ga doping concentration of 1020 cm-3 using metal-organic chemical vapor deposition technique. Crystalline structures of as-grown and post-annealed samples are studied by x-ray diffraction technique. Their transparency is also tracked by n & k analyzer. Under optimized growth parameters, the lowest resistivity of GZO is 5.5 × 10-4 ohm-cm.