Optically excited mos-capacitor for recombination lifetime measurement

Carrier recombination lifetime measurements have always been a challenging task when performed on epitaxial layers. This is due to the fact that most techniques determine the lifetime value by measuring the minority carriers' diffusion length. We will present a new method for measuring the lifetime parameter using light excitation on a MOS-capacitor that is biased into heavy inversion. The annihilation of the optically generated carriers under the shield of an existing depletion region simplifies the mathematical analysis. We show that our proposed approach, corroborated by experimental results, is capable of monitoring lifetime variations due to the presence of metallic impurities as low as 10¹⁰cm^-3.