Conversion pathways of primary defects by annealing in proton-irradiated n -type 4H -SiC

Abstract

The development of defect populations after proton irradiation of n-type 4H-SiC and subsequent annealing experiments is studied by means of deep level transient (DLTS) and photoluminescence spectroscopy. A comprehensive model is suggested describing the evolution and interconversion of irradiation-induced point defects during annealing below 1000 • C. The model proposes the EH 4 and EH 5 traps frequently found by DLTS to originate from the (+/0) charge transition level belonging to different configurations of the carbon antisitecarbon vacancy (CAV) complex. Furthermore, we show that the transformation channel between the silicon vacancy (V Si ) and CAV is effectively blocked under n-type conditions, but becomes available in samples where the Fermi level has moved towards the center of the band gap due to irradiation-induced donor compensation. The annealing of V Si and the carbon vacancy (V C ) is shown to be dominated by recombination with residual self-interstitials at temperatures of up to 400 • C. Going to higher temperatures, a decay of the CAV pair density is reported which is closely correlated to a renewed increase of V C concentration. A conceivable explanation for this process is the dissociation of the CAV pair into separate carbon anitisites and V C defects. Lastly, the presented data supports the claim that the removal of free carriers in irradiated SiC is due to introduced compensating defects and not passivation of shallow nitrogen donors.

Theory of the Thermal Stability of Silicon Vacancies and Interstitials in 4H–SiC

“…It also has a calculated acceptor transition at E(−/0) = E c − 0.44 eV. As recently suggested by Karsthof et al [19], the first donor level is rather close to the EH 4 and EH 5 electron traps. Other potential DLTS signals that could be assigned to CAV(+/ + +) and CAV(0/+) transitions are HK4 and EM1 [65].…”

“…V C defects have relatively low formation energy, E f ∼ 5 eV, thus explaining their presence in as-grown epi-layers-they are thermally generated and left "frozen" in the layers upon cooling from growth conditions (usually above 1200 • C) [18]. EH 4 and EH 5 traps were recently assigned to a carbon-related antisite-vacancy (CAV) pair [19], an isomer of the silicon vacancy (V Si ) [20][21][22]. The key arguments for the assignment were that (i) the introduction rates of both EH 4 and EH 5 clearly displayed a linear dependence with the proton fluence, and they were approximately the same as (although slightly and systematically lower than) isolated V C and V Si .…”

Muon Interaction with Negative- U and High-Spin-State Defects: Differentiating Between C and Si

“…1(b)] that has previously been attributed to the divacancy [48]. Its appearance can be attributed to the increased annealing temperature at which V Si becomes more mobile and hence facilitates the formation of the divacancy [49]. The annealing of the samples at 300 • C, on the other hand, is not sufficient to promote this mechanism.…”

Resolving Jahn-Teller induced vibronic fine structure of silicon vacancy quantum emission in silicon carbide

“…A more likely explanation related to a reduction of nonradiative channels due to out-annealing of implantation damage must therefore be considered (see, e.g., Ref. [44] for a related discussion). The different responses of V1 and V1 ′ to temperature (see Supplemental Material at [40] for detailed illustration with background subtraction), on the other hand, are more challenging to explain according to this theory.…”