Measurements of the recombination radiation were performed on cross-cuts of forward-biased rectifiers and thyristors made from silicon. Such measurements make it possible to estimate how the recombination is distributed between the swamped middle region and the highly doped border regions. It was found that in standard devices already at the operation current densities of the order of 100 A/cm2 the recombination takes place mainly in the highly doped border regions. At surge current densities of 1000 A/cm2 and more the contribution of the middle region almost vanishes. Exceptions are, at least at current densities below surge current levels, devices that are strongly doped with gold.
