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

Abstract

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.

Variable-wavelength frequency-domain terahertz ellipsometry

“…[17][18][19][20] Ellipsometry in the terahertz frequency domain, however, is still in its infancy and experimental reports are scarce. [21][22][23][24][25][26] Nagashima and Hangyo 21 demonstrated the first ellipsometry setup operating in the terahertz frequency range. By augmenting a terahertz time-domain spectrometer by fixed polarizers the p and s-polarized reflectivities and thereby the complex optical constants of a moderately phosphorousdoped n-type silicon substrate were determined.…”

“…23,24 Recently, we employed the frequency-domain terahertz ellipsometer setup which is described here in detail for the determination of free chargecarrier diffusion profiles in silicon. 25 Here we describe a novel wavelength-tunable frequencydomain ellipsometry setup operating in the spectral range from 0.2 to 1.5 THz. In order to illustrate our terahertz ellipsometry setup, describe the measurement algorithm, and discuss the data analysis procedures we have selected silicon substrates with different free charge-carrier properties as a simple model system.…”

Dual-modulator broadband infrared Mueller matrix ellipsometry

“…Infrared (IR) ellipsometry [3][4][5][6] is a powerful variant of this technique due to its capability of determining optical properties for specific vibrational resonances, thereby providing local structural information for a targeted chemical moiety. There have been accounts of such experiments in the near-IR [7], mid-IR [2,6,[8][9][10][11][12][13][14][15][16][17], far IR [18][19][20][21][22], and terahertz [23][24][25][26][27] regions. Of particular interest are ellipsometers that modify polarization states using photoelastic modulators (PEMs) [28][29][30].…”

Infrared spectroscopic ellipsometry study of sulfur-doped In0.53Ga0.47As ultra-shallow junctions

“…The infrared dielectric function of a doped layer is dominated by free carrier absorption from which parameters such as electrical resistivity q, carrier relaxation time s, and N can be determined using a classical Drude model. 13 The thickness of the doped layer t obtained from ellipsometry could be related to the junction depth. R s is calculated from q and t of the doped layer.…”

“…Additionally, knowledge of the effective mass of the band involved in conduction may allow us to extract the doping profile. 13,14 Infrared ellipsometry was applied to characterize sub-100 nm Si junctions formed by excimer laser annealing on bulk Si and Si-on-insulator. 15 R s values for junction depths down to $30 nm were reported.…”