EPR and theoretical studies of negatively charged carbon vacancy in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mn>4</mml:mn><mml:mi>H</mml:mi><mml:mtext>−</mml:mtext><mml:mi mathvariant="normal">Si</mml:mi><mml:mi mathvariant="normal">C</mml:mi></mml:mrow></mml:math>

Umeda, T.; Ishitsuka, Yosuke; Isoya, Junichi; Son, N. T.; Janzén, Erik; Morishita, Norio; Ohshima, Takeshi; Itoh, Hisayoshi; Gali, Ádám

doi:10.1103/physrevb.71.193202

Cited by 59 publications

(84 citation statements)

References 19 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%

“…In later studies [83,84], the reduction of the concentration of Z 1 /Z 2 by C implantation and subsequent annealing was observed, supporting the suggestion that these centers are V Crelated defects. In EPR studies, the C vacancies in the single positive charge state ( ) at both the k and h sites [40] and in the single negative charge state ( at the h site [41] have been identified. The carbon vacancies are very thermally stable and have similar annealing behaviors as the Z 1 /Z 2 center [85].…”

Section: Negative-u Center Z 1 /Z 2 In 4h-sicmentioning

confidence: 99%

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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%

Section: Negative-u Center Z 1 /Z 2 In 4h-sicmentioning

confidence: 99%

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

Trinh¹

2015

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“…From the obtained g tensor and the Si hyperfine (hf) tensors, the spectra were identified to be V À C signals at the cubic site (V À C ðkÞ) and at the hexagonal site (V À C ðhÞ). 14,24 Under illumination, the V À C ðhÞ signal clearly increased and the V À C ðkÞ signal appeared, which can be explained by negative-U nature of V C . 13,14 In equilibrium for n-type SiC, V À C prefers capturing another electron to relax to the lower-lying 2-state which is EPR inactive.…”

Section: B Depth Profiles Of Z 1=2 Center After Electron Irradiationmentioning

confidence: 95%

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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“…Both lines are dramatically enhanced by illumination with energies hν~1.3 eV. The higher field line is from  C V (h) [4] and the new line at a slightly lower field was previously assumed to be related to…”

Section: 3mentioning

confidence: 96%

“…In a previous electron paramagnetic resonance (EPR) study of n-type 4H-SiC substrates irradiated by high-energy (2 MeV) electrons, only the negative carbon vacancy at the hexagonal site,  C V (h), was identified [4]. In a recent study of high-doped n-type 4H-SiC freestanding layers irradiated by low-energy (250 keV) electrons, which create defects mainly in the C sublattice such as C vacancies, C interstitials and their associated complexes, two dominant EPR signals,  C V (h) and a new center, have been observed [5].…”

Section: Introductionmentioning

confidence: 99%

Identification of the Negative Carbon Vacancy at Quasi-Cubic Site in 4H-SiC by EPR and Theoretical Calculations

Trinh

Szász

Hornos

et al. 2014

MSF

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Abstract. In freestanding n-type 4H-SiC epilayers irradiated with low-energy (250 keV) electrons at room temperature, the electron paramagnetic resonance (EPR) spectrum of the negative carbon vacancy at the hexagonal site,  C V (h), and a new signal were observed. From the similarity in defect formation and the spin-Hamiltonian parameters of the two defects, the new center is suggested to be the negative C vacancy at the quasi-cubic site,

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EPR and theoretical studies of negatively charged carbon vacancy in4H−SiC

Cited by 59 publications

References 19 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

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

Identification of the Negative Carbon Vacancy at Quasi-Cubic Site in 4H-SiC by EPR and Theoretical Calculations

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