The emission spectra of avalanching n+p junctions manufactured in a standard 350-nm CMOS technology with no process modifications are measured over a broad spectral range and at different current levels. In contrast to the narrow-band forward-biased pn junction emission spectrum, the reverse biased avalanching emission spectrum extends from the ultraviolet 350 nm (3.6 eV) to the near infrared 1.7 μm(0.7 eV), covering the visual range. The photon emission energy spectrum is compared to the hot electron energy distribution within the conduction band, as determined from a full band Monte Carlo simulation. This allows the identification of phonon assisted indirect intraband (c-c) hot electron transitions as the dominant physical light emission processes within the high electric field avalanching junction. Device simulations are utilized to identify the device drift region as the source of the near infrared emissions.