What is leakage current in an LED?
The term leakage is applied to reverse biased diodes because ideally the current would be zero.  Saturation means more input doesn't cause a change.  So the leakage current is also referred to as saturation current because it is fairly independent of the amount of reverse bias.  It is not, however, independent of carriers generated by other sources of energy.  If the diode is heated or light is shined on it, more carriers will be freed up to contribute increasing the reverse saturation current.  The limit of leakage current has to do with the limited number of minority carries near the junction.