Determination of charge carrier concentration in n- and p-doped SiC based on optical absorption measurements

Abstract

We have investigated the effect of doping on absorption for various SiC polytypes, i.e., n-type (N) 6H–SiC, 4H–SiC, and 15R–SiC, p-type (Al) 6H–SiC, and 4H–SiC, and p-type (B) 6H–SiC. For these polytypes the band-gap narrowing with higher doping concentration is observed. In addition, for n-type doping below band-gap absorption bands at 464 nm for 4H–SiC, at 623 nm for 6H–SiC, and at 422 and 734 nm for 15R–SiC are observed. The peak intensities of these absorption bands show a linear relation to the charge carrier concentration obtained from Hall measurements. The corresponding calibration factors are given. As an application a purely optical wafer mapping of the spatial variation of the charge carrier concentration is demonstrated.

Investigation of the charge carrier concentration in highly aluminum doped SiC using Raman scattering

“…Unfortunately, a mapping of samples with hole concentrations in the technological relevant range of p > 10 19 cm -3 is not reasonable because of the high error of 50 %. Optical absorption at lower aluminum concentrations shows typical charge carrier variations of about 20 % [4]; therefore, variations in this range cannot be resolved with the presented method if the signal/noise ratio of the spectra cannot be raised.…”

“…The standard method to determine these properties, temperature dependant Hall effect measurements, is intricate, time consuming, and destructive. Therefore, optical approaches have been employed in the past [4,5]. Optical methods have the advantage of being non-destructive and relatively fast.…”

Influence of dislocation content on the quantitative determination of the doping level distribution in n-GaAs using absorption mapping

“…Absorption will depend on the band structure and manifest itself as a result of either (i) valence to conduction band transitions (fundamental absorption), (ii) transitions between acceptor levels and conduction band and transitions between valence band and donor levels (below band gap absorption) and (iii) free carrier absorption resulting from intra valence band transitions (as discussed for SiC in [2,3]). Concerning its fundamental absorption (i) GaAs shows a doping level induced band gap shift.…”

Bulk growth of SiC – review on advances of SiC vapor growth for improved doping and systematic study on dislocation evolution

“…Both low and high doped n-and p-type crystals were evaluated regarding basal plane dislocations. The doping concentration in both doping types was in the range n, p = 10 16 -10 19 cm -3 for the purely n-and p-type doped crystals and about 10 17 -10 18 cm -3 (p-and n-type doped regions) for the sequentially p-type/n-type/p-type doped ones as determined by optical absorption [31] and Hall measurements [32]. The seed crystals used in the growths were n-type doped (n ≈ 2 × 10 17 cm…”