Micro-Raman investigation of p-type B doped Si(1 0 0) revisited

Abstract

The doping concentration of B doped single-crystal Czochralski Si(1 0 0) wafers (6 × 1014-5 × 1019 cm−3) has been monitored via micro-Raman spectroscopy using visible (633 and 532 nm) and near-UV (355 nm) laser excitations at low power (5 mW). Data have been analysed with unprecedented accuracy via a convoluted Fano-Gaussian model of the first-order Raman Stokes mode of Silicon. This allowed the determination of the fitting spectral parameters (peak position and width) with an accuracy of 0.01 cm−1, which enables a reliable probing of the concentration. We observed, independently on the excitation wavelength used, a widening (up to 6.5 cm−1), a frequency-softening (up to 1.5 cm−1) and an intensity reduction (down to 90%) of the Si peak with the doping concentration. The widening and frequency-softening follow a strictly linear dependence with doping concentration, allowing a calibration. A linear dependence of the reciprocal Fano asymmetry parameter (q-1) with excitation energy is verified, with the slope showing a linear behavior with the doping concentration and providing a direct estimate on the hole-phonon interaction strength. Results are reproduced with surface-sensitive near-UV Raman spectroscopy on BF2+ ion implanted and laser thermal annealed (LTA) Si, demonstrating the full portability of the Raman technique to state-of-the-art nanoelectronics.