Study of the Charge Carrier Collection Coefficient of Silicon p-i-n Photodiodes

Abstract

The paper investigates the collection coefficient of minority charge carriers in silicon p-i-n photodiodes and the influence of certain technological factors on it. It has been found that the diffusion length of minority charge carriers and the resistivity of the material have a significant effect on the value of the collection coefficient, since the collection area of photogenerated charge carriers increases with increasing these parameters. It was also found that an effective method to increase the collection coefficient of photodiodes is to ensure that the thickness of the high-resistance region of the photodiode is equal to the sum of the diffusion length of minority charge carriers and the width of the space charge region. The effect of the concentration of dopants on the responsivity and collection coefficient is investigated. It was found that, in contrast to the calculated data, in which the collection coefficient increases with decreasing concentrations of phosphorus and boron, in the experimental data, with decreasing concentrations of impurities, the responsivity and, accordingly, the collection coefficient decrease due to a decrease in the degree of heterogenization and, as a result, a decrease in the width of the space charge region and the diffusion length of minority charge carriers.