In forward biased junctions crystallographic defects and impurities may be the cause of three different noise sources: (a) recombination noise, (b) flicker noise and (c) burst noise. Recombination noise is shown to be lower than the full shot noise of the recombination current and measurements at intermediate frequencies are shown to be very close to the theoretical value. For flicker noise at least two kinds of sources have been proposed: dislocations or surface traps. It is shown that the effects of dislocations on flicker noise can be explained by the surface model. Finally, the physical sources of burst noise are investigated. From statistical experiments carried out on several dozens of wafers it is concluded that crystallographic defects are the main source of burst noise.