MODELING AND MEASUREMENTS OF GENERATION AND RECOMBINATION CURRENTS IN THIN-FILM SOI GATED-DIODES

摘要

A systematic analysis of generation and recombination current behavior in a thin-film SOI gated-diode, based on an accurate modeling of volume and surface g-r components, is presented. It is shown that, for the case of the thin-film SOI devices, the gated-diode measurements should be interpreted with a great care. There are two types of conditions when data interpretation is simplified and does not require any numerical simulation. One of them is realized when the difference between front and back surface potentials is kept small, that is, at the conditions close to double-gate regime. Then volume and both surface g-r components exhibit similar gate-voltage dependencies being suppressed in accumulation and inversion and maximum in depletion. In this case, the maximum experimental forward (or reverse) current can be used for the extraction of the effective recombination (or generation) lifetime, which will involve the maximum contributions from the Si film volume and both surfaces. The data analysis is also simplified for the conditions when one of interfaces is in strong inversion, while the other one is in strong accumulation. As this takes place, the contributions from both interfaces are eliminated, and the overall g-r current in the Si film can be expressed assuming a linear potential variation across the film thickness. In this case, the lifetime value extracted from the experimental reverse or forward current should reflect the quality of the Si film. Using the gated-diode method, it has been shown that in thin-film UNIBOND SOI devices generation and recombination currents are entirely determined by interfaces with a negligible contribution from the Si film volume, which confirms the high quality of UNIBOND wafers.