Quantification of nanospreading resistance profiling data

Abstract
In nanospreading resistance, the resistance measured at a particular position on the sample cross section is not exclusively determined by the carrier concentration at this position, but by the entire surrounding carrier profile. The correct evaluation of this spreading effect requires a detailed calculation, leading to a deconvolution algorithm, which recovers the charge-carrier profile from the measured resistance profile. In this work, a general scheme for transforming a wide range of profiles is proposed. The scheme is based upon finite-element calculations of the potential distribution and the current spreading of a circular flat contact current source on a semi-infinite semiconductor sample with known carrier distribution. A correction factor database is formed as a function of typical profile characteristics such as (i) the distance to perfectly isolating or conducting boundaries, (ii) carrier gradient, and (iii) carrier curvature. In routine operation the transformation of resistance data into the carrier-concentration profile is done by interpolation of the database, hereby avoiding the time-consuming finite-element calculations. The latter results in a very fast calculation of the carrier profile data with an accuracy better than 10%, without any loss in spatial resolution. Examples are given that illustrate the accuracy of the method.

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