The noise pulse rate of microplasmas and uniform avalanche diodes is determined by carrier generation within the space‐charge layer of the breakdown region, and by minority carrier diffusion to the breakdown region. By suppressing the minority carrier diffusion from bulk to breakdown region with a suitable geometry, it is possible to investigate the carrier generation within the space‐charge layer of ap‐njunction. Three contributions to the carrier generation rate are found: (1) thermal carriers from generation centers, (2) re‐emission of carriers trapped during preceding periods of avalanche breakdown, and (3) carrier generation by internal field emission (band‐to‐band tunneling). For the case of uniform avalanche diodes, these three contributions are investigated separately. The density of generation and trapping centers within the breakdown region could be reduced by several orders of magnitude by driving the diodes into secondary breakdown. During this process the breakdown region is heated to a temperature of the order of 1000°C at which trapping and generation centers are partly annealed.