This paper presents the fabrication and characterization of GaN/Si based Ultraviolet (UV) Metal/Semiconductor/Metal (MSM) photodetectors. The thin GaN membranes have been obtained by semiconductor micromachining techniques. The two MSM interdigitated structures are contrived of fingers and interdigit spacings 100 and 200 nm wide respectively, obtained by nanolithographic techniques on GaN. Responsivity measurements were performed using both front side as well as backside-illumination. For front side illumination and for a wavelength of 365 nm and 2.5 V bias the structure with 100 nm wide fingers/interdigit spacing, exhibited the high value of 1.45 A/W. Backside-illumination responsivity of the same structure was similar to 0.37 A/W at the same wavelength and bias. Backside-illuminated photodetctors are interesting in two dimensional UV CCD imaging array manufacturing. (C) 2011 Elsevier B.V. All rights reserved.