Hole diffusion profile in a p-p+ silicon homojunction determined by terahertz and midinfrared spectroscopic ellipsometry

Noninvasive optical measurement of hole diffusion profiles in p-p+ silicon homojunction is reported by ellipsometry in the terahertz (0.2–1.5 THz) and midinfrared (9–50 THz) spectral regions. In the terahertz region a surface-guided wave resonance with transverse-electrical polarization is observed at the boundary of the p-p+ homojunction, and which is found to be extremely sensitive to the low-doped p-type carrier concentration as well as to the hole diffusion profile within the p-p+ homojunction. Effective mass approximations allow determination of homojunction hole concentrations as p=2.9×1015 cm−3, p+=5.6×1018 cm−3, and diffusion time constant Dt=7.7×10−3 μm2, in agreement with previous electrical investigations.