Application of Open Circuit Voltage Decay to the Characterization of p/n+ and n/p+ Epitaxial Layer

High quality silicon epitaxial layers are inevitable in bipolar and/or unipolar technology. However, its properties are not as easy characterized as those of bulk material. The recombination lifetime is dominated by surface/interface recombination for thin layers, which epitaxial ones generally are. We have designed diode structure with n+n/p+and  p+p/n+ epitaxial layer for open circuit voltage decay (OCVD) technigue. In such a structure, injected carriers are constrained within lightly doped base by potential barriers of junction and high-low contact and their concentration can then decrease only by recombination. Carrier lifetime obtained by this manner yields information mainly about the defect properties of epitaxial layer. Performing OCVD measurement for high-level injection condition, also tn and tp could be evaluated