Investigation on origin of Z1/2 center in SiC by deep level transient spectroscopy and electron paramagnetic resonance

Kawahara, Koutarou; Trinh, Xuan Thang; Són, Nguyên Tiên; Janzén, Erik; Suda, Jun; Kimoto, Tsunenobu

doi:10.1063/1.4796141

Cited by 60 publications

(45 citation statements)

References 20 publications

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“…13 Based on the correlation between the energy position in the bandgap of the Z 1=2 center determined by deep level transient spectroscopy (DLTS) and that of V C by electron paramagnetic resonance (EPR), the Z 1=2 center was assigned to the (2-/0) level of V C . 14 Furthermore, it has been shown that the Z 1=2 center and V C defect are the dominant defects and are responsible for carrier compensation in electron irradiated SiC, 15 further supporting that the Z 1=2 center originates from V C . Even by these continuous studies, however, a direct quantitative evidence showing the origin of the Z 1=2 center has not been achieved.…”

Section: Introductionmentioning

confidence: 92%

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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Section: Introductionmentioning

confidence: 92%

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 the present study, using layers with both sides irradiated to avoid the interference of the signals of the N donors, EPR studies can be performed also at low temperatures. Combining EPR results obtained in a wide temperature range and theoretical calculations of the ligand hyperfine constants of V at two equivalent lattice sites, we identify the new EPR signal as the negative C vacancy at the quasi-cubic site, V (k), and consolidate the previous assignment of V as the origin of the Z1/Z2 negative-U defect [5,6].…”

Section: Introductionmentioning

confidence: 96%

“…After irradiation, the layers become semi-insulating with the Fermi level located at ~0.53 eV below the conduction band [6]. The EPR spectrum measured at 6 K in darkness shows only the SI-1 signal [7] [ Fig.…”

Section: 3mentioning

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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“…Using high n-type doping 4H-SiC irradiated with high electron fluences it was possible to apply EPR and DLTS on the same samples, allowing direct correlation between Z 1 /Z 2 concentration determined by DLTS and the concentration determined by EPR. Combining DLTS, EPR and supercell calculations, we show that the Z 1 /Z 2 deep level is related to the (2-|0) level of V C [42,86,87] and the higher-lying levels Z 1 and Z 2 are the (-|0) levels of V C at h and k sites, respectively [42,43].…”

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

confidence: 99%

“…In our present studies [42,43,86,87], we used low-energy (250 keV) electrons to irradiate free-standing 4H-SiC CVD layers at room temperature to displace mainly carbon atoms. Combining EPR experiments and the supercell calculations, the (k) was identified [43].…”

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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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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Investigation on origin of Z1/2 center in SiC by deep level transient spectroscopy and electron paramagnetic resonance

Cited by 60 publications

References 20 publications

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

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

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