Temporal decay of photon emission from avalanche photodiodes (APDs) is demonstrated. The steep rise of the reverse voltage can cause a higher probability of photon emission. For a silicon avalanche photodiode, the photon emission has a broad spectral distribution from 500 to 1100 nm with two peaks at 750 and 994 nm, respectively. The number of emitted photons increases by 44 Mcount/(s mA sr) as the APD's reverse current increases. This suggests that the reverse current, instead of the reverse voltage, applied to the APD is the main determinant of the photon emission. It is furthermore shown that the distribution of the photon emission is a super-Poisson distribution.