Accurate Extraction of Minority Carrier Lifetimes—Part II: Combined I–V C–V Methods

Many optoelectronic applications require precise knowledge of minority carrier lifetimes and diffusion lengths to ensure well-defined device characteristics under operation. To extract the minority carrier lifetimes, various methods have been proposed. For instance, current–voltage (
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–
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) and capacitance–voltage (
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–
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) measurements have been used in combination (cIVCV) to extract carrier lifetimes. However, some of the proposed methods rely on approximations and simplifications that do not necessarily hold for every real device. In this work, the basic theory for the
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–
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and
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–
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relations in p-n junctions is reviewed, and accurate extraction procedures for the generation and recombination lifetime out of the reverse and forward
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and
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–
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characteristics of p-n junctions are discussed in detail. Our results demonstrate that the minority carrier recombination lifetimes extracted by the cIVCV method are significantly lower than the results from the transient methods presented in Part I. By means of computer simulations, we can show that this can be related to the interface between the epitaxial layer and the substrate, which is modeled using an effective surface recombination velocity. Furthermore, our results outline the main difference between the open-circuit voltage decay (OCVD) and reverse recovery (RR) method presented in Part I where carrier recombination at the back surface plays an important role on one side and the cIVCV method where the main signal originates from the p-n junction depletion zone and is, therefore, less affected by the back surface on the other side.