This paper reports the thermo-phototronic effect in a 3C-SiC/Si heterostructure, showing a significant enhancement in the sensitivity of a photodetector. The first step is the fabrication of a photodetector with a 3C-SiC/Si heterostructure sensing element from a silicon wafer via a photolithography process. Next, the photodetecting behavior was examined in a temperature gradient under illumination with different light intensities. The photodetector can harvest the energy from light and convert it to electrical energy to power itself and detect the light with intensity from 12,000 lx to 34,000 lx. The temperature of one electrode was increased to create the temperature gradient to enhance the lateral photovoltage. The generated voltages were improved at higher temperatures and reached up to around 147% enhancement when a temperature of 150°C is applied to an electrode. These results demonstrate the potential of using thermo-phototronic effect of SiC/Si heterostructure for ultrasensitive self-powered photodetectors.