Well-defined Dahlia type gallium nitride flowers (GaNFs) have been synthesized on c-plane sapphire substrates at different growth conditions using chemical vapour deposition system. The growth was carried out without any catalyst medium for favouring the nucleation process. Crystal structure of the GaNFs was obtained using x-ray diffractometer (XRD). Scanning electron microscopy (SEM) revealed the morphology of GaNFs. The elemental traces and compositions of the samples were obtained using energy dispersive x-ray (EDX) spectroscopy and x-ray photoelectron spectroscopy (XPS). The optical properties of the samples were analysed using cathodoluminescence (CL) spectroscopy and Raman spectroscopy. From the current-voltage (I-V) response, it was observed that there are no interface and surface related inhomogeneities in the samples. The fabricated photodetector showcased good device performance due to high carrier density in the sample.