Optoelectronic saturation behavior of a p-n junction

Optoelectronic saturation in a p-n junction can be advantageously used to analyze the anomalous electrical behavior of nonideal p-n junction devices. The relevant saturation occurs in the photocurrent delivered to a load as a result of increases in the externally imposed optical illumination or electrical bias, which are sufficient to cause forward-biased conduction of the p-n junction. Analysis shows that the degree of saturation is best measured by changes in an optically generated derivative of the load current and that this derivative can be effectively used to evaluate the electrical characteristics of the junction. Experimental measurements based on conventional derivative techniques confirm the analysis and illustrate its utility by directly evaluating the equivalent circuits for some well-behaved but nonideal junction diodes.