Modified Pulsed MOS Capacitor for Characterization of Ultraclean Thin ${\rm p}/{\rm p}^{+}$ Silicon Epitaxial Layers

We develop a modified pulsed MOS technique for measuring generation lifetime in ultraclean and thin
${\rm p}/{\rm p}^{+}$
epitaxial layers, which can be used to detect metallic impurities with densities as low as
$10^{10}{\rm cm}^{-3}$
. The widely used classic version is shown to be unable to effectively detect such low impurity densities because of the domination of surface generation; whereas, recombination lifetime measurement techniques have serious limitations for layers that have smaller thicknesses than the minority carrier diffusion length.