Effects of film thickness and electrode spacing on the performance of Ga2O3 MSM UV-C photodetectors for optical communication

Metal-semiconductor-metal (MSM) UV-C detectors have been fabricated on RF sputtered n-type a-Ga 2 O 3 films with thicknesses of 20 – 220 nm and electrode separations of 5 – 80 μm. Increased film thickness led to performance improvements with responsivity of 7.85 A/W and detectivity of 1.28 × 10 13 Jones exhibited by a device formed on the thickest film. Response (rise and fall) time increased moderately with thickness. The separation of the dual contacts in the MSM device determined the transit time but charge-trapping effects most influenced the response times. Encapsulation minimised the effects of surface adsorption/desorption on surface electronic properties and thus stabilised the photo-responses of the devices. Finally, short range transmission and reception of Morse-coded UV-C signals was demonstrated to highlight the potential for low-cost a-Ga 2 O 3 based MSM photodetectors to enable UV-C communications.