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 μ m², in agreement with previous electrical investigations.