We have considered 6H and 4H SiC n-MOSFETs from two different origins and studied the photon emission coming from the channel of the devices biased in the saturation regime. We have simultaneously measured the drain and the substrate currents, which enabled us to establish a specific relationship between the currents and the emission intensity. Additionally, we performed a spectral analysis which clearly indicates the contribution of one or more recombination center(s) inside the bandgap of silicon carbide.