A technique for accurate FTIR determination of boron concentration in CVD homoepitaxial diamond layers

The significant technology progress for fabrication of semiconducting CVD diamonds poses an important task of developing a precise and non-destructive method for estimation the boron content in epitaxial layers. We propose a novel two-step technique to determine the boron concentration in homoepitaxial diamond layers from FTIR measurements. The essence of the method is to evaluate the epilayer thickness from reflectance spectra at the first step, and to recalculate and analyze FTIR spectra in terms of effective optical density at the second step. Spectra are divided into 3 wavelength regions with accurate accounting of passing radiation through a multilayered structure with different thicknesses of absorbing media for various absorbing mechanisms. We have demonstrated the benefit of the method for a set of samples with CVD homoepitaxial layers grown on various HPHT substrates. The data obtained from FTIR spectra are thoroughly compared to the charge carrier concentration derived from electrical capacitance–voltage measurements.