EFFECTS OF DIFFUSION-INDUCED DEFECTS ON THE CARRIER LIFETIME

Among the wafer processing steps which occur in the fabrication of p-i-n diodes, the heavy introduction of dopants in the end regions is one of the Major sources of crystal defects. Two different p+-end diffusion processes have been characterized: one with boron, the other with boron and aluminium. The electron beam induced current technique has been utilized to delineate the electrically active defects and to determine the minority carrier lifetime, tau, in the base and in the emitter region of the device. The open circuit voltage decay method has also been applied to measure tau in the base region and the two sets of measurements have been qualitatively compared to assess the reliability of the second method. A combined analysis of the delineated electrically active defects and of the tau values obtained, has provided an indication for the beneficial effect of Al as a codifussed species in the emitter.