Generation-recombination noise in highly asymmetrical p-n junctions

A previous theory for the current noise associated with carrier generation and recombination in the space-charge region of p-n junctions is recalculated for the case of a highly asymmetrical distribution of dopant impurities. We propose a model based on the true concentrations of electrons and holes and electric field in the space-charge layer. Carriers coming from the highly doped region create a layer of mobile charge in the depletion region of the less-doped zone. This charge, usually studied under forward-bias conditions, is neglected under reverse voltages. We have demonstrated that this mobile-charge layer, although located in a very tiny region compared to the width of the space-charge layer, is crucial in the study of charge fluctuations stimulated by generation-recombination centers. Experimental results have been successfully reproduced with our theory for reverse-biased p ⁺-n diodes with deep centers located close to the metallurgical junction.