Realization of a Self-Powered InGaZnO MSM UV Photodetector Using Localized Surface Fluorine Plasma Treatment

Metal–semiconductor–metal (MSM) photodetectors (PDs) are used for optoelectronic integrated circuits (OEICs) because they allow easy integration with a pre-existing circuit. However, traditional MSM PDs require an external bias to separate the electron–hole pairs because they have a symmetrical structure. This study proposes a method to create an asymmetric Schottky barrier height in a MSM PD with a symmetrical interdigital electrode. A localized surface fluorine plasma treatment is applied to a specific area of the a-IGZO film underneath the contacts of the MSM PDs, which produces a localized oxygen deficiency. The photocurrent spontaneously diffuses because there is an asymmetric Schottky barrier. This gives the device self-powering characteristics. The a-IGZO MSM PD with a symmetrical interdigitate electrode operates at a zero bias and has a responsivity of 5 mA/W. The open-circuit voltage under illumination at 365 nm (2 mW/cm2) is 0.20 V. This study demonstrates that this method is applicable to other MSM PDs, particularly those that use an amorphous oxide semiconductor as the active layer.