Characterization of deep levels in 6H-SiC by optical-capacitance-transient spectroscopy

Abstract

An optical-capacitance-transient spectroscopy (O-CTS) method was used to characterize defects in epitaxial 6H-SiC. The O-CTS measurements enable us to estimate the optical ionization energy and the optical cross section of these defects. By the deep level transient spectroscopy (DLTS), three peaks were observed, and two of them were identified as E2 and R centers which have been previously reported. We measured the optical cross section for both the centers. By fitting the experimental data with theoretical curves for the optical cross section, we obtained optical ionization energy of 1.58 eV for the R center and 1.0 eV for the E2 center. From the DLTS measurements, the thermal activation energy of the R center is 1.30 eV and that of the E2 center is 0.43 eV. From these results and the previously reported capture energy barrier, the Franck–Condon shift, dFC is estimated to be 0.28 eV for the R center and 0.62 eV for the E2 center.

Alternative electronic parts for multiphonon-broadened photoionization cross sections of deep levels in SiC

“…This agrees also with the earlier fit by Nakakura et al 77 of the ͑h Ͼ 1.29 eV, 370 K͒ data for the R center in 6H-SiC via the approximate classical convolution integral of Chantre et al, 52 the electronic part of which is essentially Inkson's model, too. ͑5͒, the only one offering physically acceptable descriptions is that for allowed transitions ͑f =0͒ associated with a ␦-function-like trap potential ͑n =2͒.…”

“…These are ͑a͒ the ͑h Ͼ 1.29 eV, 370 K͒ data of Nakakura et al 77 ͓Fig. A survey of the literature published in the last five years yielded only two papers that presented experimental measurements of fine enough detail and broad enough range to allow meaningful tests of our analytical models.…”

“…For deep traps in SiC, some ͑h , T͒ spectra have been measured by various conventional experimental techniques such as optical absorption, [69][70][71] photocapacitance, [72][73][74] and photoconductivity 75 measurements, or by the more recently developed optical-capacitance-transient spectroscopy ͑O-CTS͒ method. [76][77][78] Estimated values for FC shifts, which were obtained by provisional fittings of the measured ͑h , T͒ data, are seen to vary over a rather broad range, extending from about 0.1 eV ͓for the so-called ND1 center in 3C-SiC ͑Ref. 76͔͒ up to about 1 eV ͑Refs.…”

“…II͒. We then fit the photoionization cross-section data ͑a͒ from Nakakura et al 77 for the so-called R center 5,6,13-15 ͑E7 center 20 ͒ in 6H-SiC and ͑b͒ from Rechanov and Rastegaev 75 for a vanadium-related level in a mixed 4H / 6H-SiC sample ͑Sec. Eq.…”

Efficiency of a solar cell with intermediate energy levels: An example study on hydrogen implanted Si solar cells

“…In the O-CTS measurements, we detected the capacitance-transient signal of a diode caused by the optical excitation of carriers from deep levels, and the signal was converted to an O-CTS spectrum by the rate window scan method. 27,28 For the excitation light, a 300 W Xe lamp was employed. The light was passed through a monochromator and focused onto the Schottky contact region.…”