Capacitance transient study of a bistable deep level in e−-irradiated n-type 4H–SiC

Using capacitance transient techniques, a bistable centre, called FB centre here, was observed in electron irradiated 4H–SiC. In configuration A, the deep level known as EH5 (Ea = EC − 1.07 eV) is detected in the deep level transient spectroscopy spectrum, whereas for configuration B no obvious deep level is observed in the accessible part of the band gap. Isochronal annealing revealed the transition temperatures to be TA → B > 730 K and for the opposite process TB → A ≈ 710 K. The energy needed to conduct the transformations were determined to be EA(A → B) = (2.1 ± 0.1) eV and EA(B → A) = (2.3 ± 0.1) eV, respectively. The pre-factor indicated an atomic jump process for the opposite transition A → B and a charge carrier-emission dominated process in the case of B → A. Minority charge carrier injection enhanced the transformation from configuration B to configuration A by lowering the transition barrier by about 1.4 eV. Since the bistable FB centre is already present after low-energy electron irradiation (200 keV), it is likely related to carbon.

Source:IOPscience

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Thermally stimulated luminescence in full-size 4H-SiC wafers

We performed non-contact and non-destructive spatially resolved characterization of traps and recombination centres in two-inch-diameter p-type 4H-SiC wafers using thermally stimulated luminescence (TSL) and scanning room temperature photoluminescence (PL). The TSL glow-curve maximum is located at about 190 K for the Al-doped wafers and the TSL spectrum has a maximum at 1.8 eV, which coincides with the spectrum of the 'red' PL band in the same crystal. The TSL intensity exhibits a noticeable inhomogeneity across the wafers. The spatial distribution shows a negative contrast compared to PL maps, indicating a variation of concentration of the TSL centres across the wafer. The origin of the centres is discussed.

Source:IOPscience

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