Negative-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>U</mml:mi></mml:math>carbon vacancy in 4<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>H</mml:mi></mml:math>-SiC: Assessment of charge correction schemes and identification of the negative carbon vacancy at the quasicubic site

Trinh, Xuan Thang; Szász, Krisztián; Hornos, T.; Kawahara, Koutarou; Suda, Jun; Kimoto, Tsunenobu; Gali, Ádám; Janzén, Erik; Són, Nguyên Tiên

doi:10.1103/physrevb.88.235209

Cited by 51 publications

(71 citation statements)

References 59 publications

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“…In 6H-SiC, nitrogen (N) substitutes C atoms at three inequivalent sites (h, k 1 and k 2 -sites) were detected by EPR as three N shallow donor centers having different gvalues [39]. For another example, the EPR signals of the carbon vacancies at inequivalent sites in 4H-SiC (h and k-sites) were also distinguishably observed [40][41][42][43].…”

Section: Common Polytypes Of Sicmentioning

confidence: 92%

Electron Paramagnetic Resonance studies of negative-U centers in AlGaN and SiC

Trinh¹

2015

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Silicon (Si) is the most commonly used n-type dopant in AlGaN, but the conductivity of Si-doped Al x Ga 1-x N was often reported to drop abruptly at high Al content (x>0.7) and the reason was often speculated to be due to either compensation by deep levels or self-compensation of the so-called DX (or negative-U) center. Understanding the electronic structure of Si and carrier compensation processes is the essential for improving the n-type doping of high-Al-content Al x Ga 1-x N. In our studies of Si-doped AlGaN layers grown by metal-organic chemical vapor deposition, Electron Paramagnetic Resonance (EPR) was used to study the electronic structure of Si in high-Al-content Al x Ga 1-x N.From the temperature dependence of the concentration of the Si donor on the neutral charge state E d determined by EPR, we showed that Si already forms a stable DX center in Al x Ga 1-x N with x ~0.77. However, with the Fermi level locating only ~3 meV below E d , Si still behaves as a shallow donor and high conductivity at room temperature could be achieved in Al 0.77 Ga 0.23 N:Si layers. In samples with the concentration of the residual oxygen (O) impurity larger than that of Si, we observed no carrier compensation by O in Al 0.77 Ga 0.23 N:Si layers, suggesting that at such Al content, O does not seem to hinder the n-type doping in the material. The result is presented in paper 1.In paper 2, we determined the dependence of the E DX level of Si on the Al content in Al x Ga 1-x N:Si layers (0.79≤x≤1) with the Si concentration of ~2×10 18 cm -3 and the concentrations of residual O and C impurities of about an order of magnitude lower (~1÷2×10 17 cm -3 ). We found the coexistence of two DX centers (stable and metastable ones) of Si in Al x Ga 1-x N for x≥0.84. For the stable DX center, abruptly deepening of E DX with increasing of the Al content for x≥0.83 was observed, explaining the drastic decrease of the conductivity as often reported in previous transport studies. For the metastable DX center, the E DX level remains close to E d for x=0.84÷1 (~11 meV for AlN).The Z 1 /Z 2 defect is the most common deep level revealed by Deep Level Transient Spectroscopy (DLTS) in 4H-SiC epitaxial layers grown by chemical vapor deposition (CVD). It has previously been shown by DLTS to be a negative-U system which is more stable with capturing two electrons. The center is also known to be the lifetime killer in asiv grown CVD material and, therefore, attracts much attention. Despite nearly two decades of intensive studies, including theoretical calculations and different experimental techniques, the origin of the Z 1 /Z 2 center remains unclear. EPR is known to be a powerful method for defect identification, but a direct correlation between EPR and DLTS is difficult due to different requirements on samples for each technique. Using high n-type 4H-SiC CVD free-standing layers irradiated with lowenergy (250 keV) electrons, which mainly displace carbon atoms creating C vacancies, C interstitials and their associated defects, it was possible...

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Section: Common Polytypes Of Sicmentioning

confidence: 92%

Electron Paramagnetic Resonance studies of negative-U centers in AlGaN and SiC

Trinh¹

2015

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“…The microscopic structure of isolated negatively charged silicon vacancy  Si V having T d symmetry has been identified with confidence in 3C, 4H and 6H polytypes of SiC [8,9,12], its high spin state S = 3/2 has been determined with additional ENDOR study [8]. The negative-U behavior has been found for spin S = 1/2 negative carbon vacancy (V C − ) at both hexagonal and quasi-cubic lattice sites [13]. Almost ten spin-one defects with parameters closely related to that of irradiated crystals have been revealed after quenching and thermal treatment of 6H-SiC crystals [14].…”

Section: Introductionmentioning

confidence: 97%

“…5). Like to spectra of negatively charged carbon vacancies V C -with the spin S = 1/2 in the polytype 4H-SiC [13], the ratio of intensities of satellite lines for Si 1 and Si [2][3][4] to that of the central line reaches the values 5 and 13%, respectively. The pairs of lines with the splitting similar to those of Si 2-4 lines are also observed both on low-field and high-field wings of the central part in the spectrum belonging mainly to the Ky6 defect.…”

Section: с Carbon Vacancy-related Complex Defectsmentioning

confidence: 99%

“…In this case, the principal axes of the HF interaction tensors are also oriented along the 111 direction. Since the isolated carbon vacancy has the spin S = 1/2 and as a negative-U center is detectable only under optical excitation [13], we should make the assumption that the T6 defect is complex and consists of the pair V C -X with the spin S = 3/2, where the letter Х designates still unknown atom in the vicinity of V C -. As it was predicted earlier [12], it may be the atom C or Si in the nearest tetrahedral interstitial position.…”

Section: с Carbon Vacancy-related Complex Defectsmentioning

confidence: 99%

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Thermal annealing and evolution of defects in neutron-irradiated cubic SiC

Bratus¹

2015

Semicond. Phys. Quantum Electron. Optoelectron.

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Abstract.A careful study of neutron-irradiated cubic SiC crystals (3С-SiCn) has been performed using electron paramagnetic resonance (EPR) in the course of their thermal annealing within the 200…1100 °C temperature range. Several inherent temperatures have been found for annealing and transformations of primary defects in 3С-SiCn among which there are isolated negatively charged silicon vacancy V Si  , neutral divacancy (V Si -V C ) 0 , negatively charged carbon vacancyantisite pair (V C -C Si )  and neutral carbon 100 split interstitial (CC) C 0 . It has been shown that transformation of V Si  into (V C -C Si )  complex is among the mechanisms of silicon vacancy annealing. As it has been established on the basis of the observed hyperfine structure, the secondary T6 center is characterized by the fourfold silicon coordination and assigned to the spin S = 3/2 carbon vacancy-related pair defect. The symmetry reduction of the (V C -V Si ) 0 center is attributed to local rearrangements in the neighborhood of divacancy, and its intensity variations are assigned to changes of the Fermi-level position. Two defects with similar symmetry and close values of zero-field splitting constants D, which concentrations increase by a factor of ten after annealing at 900 °С, are tentatively attributed to the 100 split interstitial (CC) C 0 and (NС) С 0 pairs.

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“…(iii) The detectable defects by EPR depend on the charge state of the defects; for V C , V À C is detectable, whereas V 2À C and V 0 C are EPR-inactive. Because the V C defect has a negative-U nature, 13,14,16 in n-type material most V C defects are either in the neutral or 2-charge states under equilibrium condition and, hence, cannot be detected by EPR. Due to the restriction (i), in a previous study, 17 electron fluences used for samples measured by DLTS were much lower than those used for samples studied by EPR, which prevented a direct comparison in concentration between the Z 1=2 deep level and the C vacancy.…”

Section: Introductionmentioning

confidence: 99%

Quantitative comparison between Z1∕2 center and carbon vacancy in 4H-SiC

Kawahara

Trinh

Són

et al. 2014

Journal of Applied Physics

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In this study, to reveal the origin of the Z(1/2) center, a lifetime killer in n-type 4H-SiC, the concentrations of the Z(1/2) center and point defects are compared in the same samples, using deep level transient spectroscopy (DLTS) and electron paramagnetic resonance (EPR). The Z(1/2) concentration in the samples is varied by irradiation with 250 keV electrons with various fluences. The concentration of a single carbon vacancy (V-C) measured by EPR under light illumination can well be explained with the Z(1/2) concentration derived from C-V and DLTS irrespective of the doping concentration and the electron fluence, indicating that the Z(1/2) center originates from a single V-C

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Negative-Ucarbon vacancy in 4H-SiC: Assessment of charge correction schemes and identification of the negative carbon vacancy at the quasicubic site

Cited by 51 publications

References 59 publications

Electron Paramagnetic Resonance studies of negative-U centers in AlGaN and SiC

Electron Paramagnetic Resonance studies of negative-U centers in AlGaN and SiC

Thermal annealing and evolution of defects in neutron-irradiated cubic SiC

Quantitative comparison between Z1∕2 center and carbon vacancy in 4H-SiC

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