Combining steady-state photo-capacitance spectra with first-principles calculations: the case of Fe and Ti in β-Ga<sub>2</sub>O<sub>3</sub>

Zimmermann, Christian; Frodason, Ymir Kalmann; Rønning, Vegard; Varley, Joel B.; Vines, Lasse

doi:10.1088/1367-2630/ab8e5b

Cited by 12 publications

(19 citation statements)

References 51 publications

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“…The extraction of trap parameters, such as activation energy, capture cross-section, and concentration was in some cases achieved by simulating the DLTS spectra using the method and software described in Ref. 36 .…”

Section: Methodsmentioning

confidence: 99%

Formation of carbon interstitial-related defect levels by thermal injection of carbon into n-type 4H-SiC

Karsthof

Bathen

Kuznetsov

et al. 2022

Journal of Applied Physics

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Electrical properties of point defects in 4H-SiC have been studied extensively, but those related to carbon interstitials (C i ) have remained elusive until now. Indeed, when introduced via ion irradiation or implantation, signatures related to C i observed by deep level transient spectroscopy (DLTS) tend to overlap with those of other primary defects, making the direct identification of C i -related levels difficult. Recent literature has suggested to assign the so-called M center, often found in as-irradiated 4H-SiC, to charge state transitions of the C i defect in different configurations. In this work, we have introduced excess carbon into low-doped ntype 150 µm thick 4H-SiC epilayers by thermal annealing, with a pyrolyzed carbon cap on the sample surface acting as a carbon source. Because the layers exhibited initially low concentrations of carbon vacancies ([V C ] = 10 11 cm −3 ), this enabled us to study the case of complete V C annihilation, and formation of defects due to excess carbon, i.e. carbon interstitials C i and their higher-order complexes. We report on the occurrence of several new levels upon C injection which are likely C i -related. Their properties are different from those found for the M center, which points towards a different microscopic identity of the detected levels. This suggests the existence of a rich variety of C i -related defects. The study will also help generating new insights into the microscopic process of V C annihilation during carbon injection processes.

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Section: Methodsmentioning

confidence: 99%

Formation of carbon interstitial-related defect levels by thermal injection of carbon into n-type 4H-SiC

Karsthof

Bathen

Kuznetsov

et al. 2022

Journal of Applied Physics

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“…DLTS measurements were carried out using a hightemperature setup operating between 77 and 700 K. The measurement frequency was 1 MHz, the pulse length was 20 ms and the pulse height 10 V at a reverse bias of −10 V. Six rate windows between 20 and 640 ms were chosen for evaluation of the transients, using a standard lock-in correlation function. The concentrations of the different levels found in the measured spectra were extracted by a numerical simulation of the transients and the resulting spectra, based on assumed (variable) values for trap energy, capture cross section, and density of the traps [25]. The lambda correction was included for increased accuracy of the thusly determined trap concentrations.…”

Section: Experimental Methodsmentioning

confidence: 99%

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

et al. 2020

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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.

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“…(ii) The E 2 center was initially suggested to be the Fe Ga defects by Ingebrigtsen et al [8] . Zimmerman et al [10] further distinguished that there are two overlapping DTLS peaks, labeled as E 2a (0.66 eV) and E 2b (0.73 eV) instead of a single E 2 . These two signatures have then been assigned to the Fe substituting Ga on a tetrahedral site (Fe GaI ) and an octahedral site (Fe GaII ), respectively, based on the energy levels and the concentration ratio [10] .…”

Section: Introduction β βmentioning

confidence: 99%

“…Zimmerman et al [10] further distinguished that there are two overlapping DTLS peaks, labeled as E 2a (0.66 eV) and E 2b (0.73 eV) instead of a single E 2 . These two signatures have then been assigned to the Fe substituting Ga on a tetrahedral site (Fe GaI ) and an octahedral site (Fe GaII ), respectively, based on the energy levels and the concentration ratio [10] . Recently, Zimmermann et al [11] provided additional evidence to support the above conclusion regarding the good agreement of absorption cross-section between first-principles calculations of the Fe Ga defect and the experimental results from steady-state photo-capacitance spectra measurements.…”

Section: Introduction β βmentioning

confidence: 99%

“…However, the calculated V O defect β β level is located at 1.67-2.46 eV (below the CBM) [13] , which is much deeper than E 3 at 1.01-1.10 eV and thus can be ruled out. Zimmerman et al [10] then assigned the E 3 center as a defect of Ti substituting Ga on an octahedral site (denoted as Ti GaII ) based on a strong correlation in concentration between the E 3 defect and the Ti ions present in the samples and a good agreement in energy position between the E 3 level and the Ti GaII defect, which is obtained by the hybrid functional calculations. So far, Fe-and Ti-related defects are considered as the most possible candidates for E 1 , E 2 , and E 3 centers not only due to the above arguments but also because they can be introduced to -Ga 2 O 3 unintentionally in fabrications.…”

Section: Introduction β βmentioning

confidence: 99%

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Clarifying the atomic origin of electron killers in β-Ga₂O₃ from the first-principles study of electron capture rates

Suo¹,

Wang²,

Li³

et al. 2022

J. Semicond.

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The emerging wide bandgap semiconductor -Ga2O3 has attracted great interest due to its promising applications for high-power electronic devices and solar-blind ultraviolet photodetectors. Deep-level defects in -Ga2O3 have been intensively studied towards improving device performance. Deep-level signatures E 1, E 2, and E 3 with energy positions of 0.55–0.63, 0.74–0.81, and 1.01–1.10 eV below the conduction band minimum have frequently been observed and extensively investigated, but their atomic origins are still under debate. In this work, we attempt to clarify these deep-level signatures from the comparison of theoretically predicted electron capture cross-sections of suggested candidates, Ti and Fe substituting Ga on a tetrahedral site (TiGaI and FeGaI) and an octahedral site (TiGaII and FeGaII), to experimentally measured results. The first-principles approach predicted electron capture cross-sections of TiGaI and TiGaII defects are 8.56 × 10–14 and 2.97 × 10–13 cm2, in good agreement with the experimental values of E 1 and E 3 centers, respectively. We, therefore, confirmed that E 1 and E 3 centers are indeed associated with TiGaI and TiGaII defects, respectively. Whereas the predicted electron capture cross-sections of FeGa defect are two orders of magnitude larger than the experimental value of the E 2, indicating E 2 may have other origins like CGa and Gai, rather than common believed FeGa.

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Combining steady-state photo-capacitance spectra with first-principles calculations: the case of Fe and Ti in β-Ga₂O₃

Cited by 12 publications

References 51 publications

Formation of carbon interstitial-related defect levels by thermal injection of carbon into n-type 4H-SiC

Formation of carbon interstitial-related defect levels by thermal injection of carbon into n-type 4H-SiC

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

Clarifying the atomic origin of electron killers in β-Ga₂O₃ from the first-principles study of electron capture rates

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Combining steady-state photo-capacitance spectra with first-principles calculations: the case of Fe and Ti in β-Ga2O3

Cited by 12 publications

References 51 publications

Formation of carbon interstitial-related defect levels by thermal injection of carbon into n-type 4H-SiC

Formation of carbon interstitial-related defect levels by thermal injection of carbon into n-type 4H-SiC

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

Clarifying the atomic origin of electron killers in β-Ga2O3 from the first-principles study of electron capture rates

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Combining steady-state photo-capacitance spectra with first-principles calculations: the case of Fe and Ti in β-Ga₂O₃

Clarifying the atomic origin of electron killers in β-Ga₂O₃ from the first-principles study of electron capture rates