The development of fifth-generation (5G) communications and the Internet of Things (IoT) has created a need for high-performance sensing networks and sensors. Improving the sensitivity and reducing the energy consumption of these sensors can improve the performance of the sensing network and conserve energy. This paper reports a large enhancement of the photovoltaic effect in a 3C-SiC/Si heterostructure and the tunability of the photovoltage under the impact of a temperature gradient, which has the potential to increase the sensitivity and reduce the energy consumption of microsensors. To start with, cubic silicon carbide (3C-SiC) was grown on a silicon wafer, and a micro-3C-SiC/Si heterostructure device was then fabricated using standard photolithography. The result revealed that the sensor could either capture light energy, transform it into electrical energy for self-power purposes, or detect light with intensities of 1.6 and 4 mW/cm2. Under the impact of the temperature gradient induced by conduction heat transfer from a heater, the measured photovoltage was improved. This thermo-phototronic coupling enhanced the photovoltage up to 51% at a temperature gradient of 8.73 K and light intensity of 4 mW/cm2. Additionally, the enhancement can be tuned by controlling the direction of the temperature gradient and the temperature difference. These findings indicate the promise of the temperature gradient in SiC/Si heterostructures for developing high-performance temperature sensors and self-powered photodetectors.