In this work, a 4H-SiC phototransistor based on an ion implantation process is demonstrated. The incorporation of a surface pn-junction structure effectively enhances the overall device responsivity, particularly in the far-UVC band, where responsivities of 100.7 A/W at 200 nm and 60.0 A/W at 240 nm are achieved. These values rank among the highest reported for SiC phototransistors operating in the same detection wavelength range. Additionally, TCAD simulations have been employed to verify the effectiveness of this new structure. These results offer a promising design strategy for fabricating high-performance SiC UV phototransistors tailored for far-UVC detection.