Detection of recombination centers in epitaxial layers by temperature scanning and depth lifetime profiling

A measurement technique based on a new test structure has been presented by P. Spirito and G. Cocorullo (IEEE Trans. Electron Devices. vol.ED-34, p.2546-54, 1987). It gives the recombination lifetime profile along thin epilayer. The capability of this test structure to extract from temperature scanning the energy distribution of minority-carrier recombination centers and their spatial distribution along thin epilayers is examined. Applications of this technique on processed n-type epilayers show that, besides a deep level, there is a second shallow level with a spatial distribution increasing toward the epilayer-substrate interface, probably outdiffused from the substrate during the epi growth. The lifetime profile of these samples is determined by the different spatial distribution of two traps levels, located at different energies inside the bandgap.<
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