Flash X-ray irradiation of P-N junctions: A method to measure minority carrier lifetimes, diffusion constants and generation constants

Abstract

A method to measure the minority carrier lifetime in semiconductors has been developed utilizing short flashes of X-rays. The advantage with the use of X-rays instead of light is that the generation of charge carriers can be made very homogenous and that the concentration of generated carriers can be varied within a wide range.The experiments were carried out on P+-N silicon diodes and concerned measurements of the decay times for radiation induced currents as function of reverse bias and width of the bulk regions of the diodes. It is shown that by plotting the decay rate as function of the inverse value of the square of the width of the bulk region (according to the theoretical model used) it is possible to obtain both the minority carrier lifetime and the diffusion constant of the N-material. Comparison with other methods confirms the usefulness of the method.By measuring the reverse bias dependence of the width of the depletion region and the corresponding variations in integrated radiation-induced current it was possible to determine the generation constant.