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1

Digitale Medien

Jenny, J. R. ; Skowronski, M. ; Mitchel, W. C. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 78 (1995), S. 3160-3163

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Low-temperature optical absorption experiments have been performed on a variety of n-type, p-type, and high-resistivity silicon carbide samples, including the polytypes: 4H, 6H, and 15R. These experiments reveal a set of absorption band close to the band edge with a fine structure depending upon the polytype. Each sample exhibits a spectrum with the number of lines corresponding to the number of inequivalent substitutional lattice sites contained in the polytype. A correlation of these lines with the neutral vanadium 2E→2T2 intracenter transition indicates that the initial state for the near-band-gap absorption lines is the 2E state of the 3d1 configuration of vanadium. The near-band-edge absorption lines were interpreted as due to an exciton bound to a vanadium donor with an electron occupying an atomic-like d state. The position of the vanadium acceptor level was estimated to be, at most, 250 meV from the conduction band for the cubic site in 6H SiC. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.360004

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2

Digitale Medien

On the compensation mechanism in high-resistivity 6H–SiC doped with vanadium (1995)

Jenny, J. R. ; Skowronski, M. ; Mitchel, W. C. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 78 (1995), S. 3839-3842

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A model is presented which describes the compensation mechanism resulting in semi-insulating 6H silicon carbide by vanadium doping. Undoped 6H–SiC crystals grown by physical vapor transport methods frequently contain between 1×1017 and 5×1018 cm−3 uncompensated boron acceptors. Upon addition of vanadium, the 3d1 electron of the vanadium donor compensates the holes of the boron centers. It is shown that when vanadium is present in concentrations greater than that of boron, the Fermi level is pinned to the vanadium donor level. From temperature dependent Hall effect measurements, this donor level has been determined to reside 1.35 eV below the conduction band minimum. Thermally stimulated current measurements on V-doped SiC crystals show that boron is the major compensating center for the vanadium impurity. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.359899

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3

Digitale Medien

Optical and electrical characterization of boron impurities in silicon carbide grown by physical vapor transport (1996)

Jenny, J. R. ; Skowronski, M. ; Mitchel, W. C. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 79 (1996), S. 2326-2331

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Undoped SiC crystals grown by physical vapor transport have been characterized by temperature dependent Hall effect and near infrared optical absorption measurements. Crystals with reduced nitrogen content were found to exhibit p-type conductivity with carrier concentrations in the 5×1014–1×1016 cm−3 range at room temperature. The Fermi level position determined from Hall effect measurements at elevated temperatures was 0.35 eV above valence band. The primary acceptor-type impurity was identified as substitutional boron with total concentration of uncompensated acceptors in the 1×1017–5×1018 range. This interpretation was confirmed by near infrared absorption spectra, which were dominated by a broad photoionization band with a threshold at 0.7 eV and a maximum at 1.75 eV. The shape of the band was fitted, and the thermal ionization energy of the defect was found to be in the 0.3–0.4 eV range. A correlation between the photoionization band intensity, and the uncompensated boron content was used to determine the value of maximum optical cross section of boron photoionization band, which was 4.17×10−17 cm2. In addition to photoionization band, boron-containing samples exhibited set of narrow absorption lines near the fundamental absorption edge. Based on correlation with boron content and line position in different SiC polytypes, these lines were identified as due to excitons bound to neutral boron acceptors. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.361158

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4

Digitale Medien

Deep level transient spectroscopic and Hall effect investigation of the position of the vanadium acceptor level in 4H and 6H SiC (1996)

Jenny, J. R. ; Skowronski, J. ; Mitchel, W. C. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 68 (1996), S. 1963-1965

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Hall effect, deep level transient spectroscopy (DLTS) and optical absorption measurements were employed in concert to determine the position of the vanadium acceptor level in vanadium and nitrogen doped 6H and 4H SiC. Hall effect results indicate that the acceptor position in 4H SiC is at 0.80 eV beneath the conduction band edge, and 0.66 eV for the 6H polytype. The DLTS signature of the defect in the 4H polytype showed an ionization energy of 0.80 eV and a capture cross section of 1.8×10−16 cm−2. The optical absorption measurements proved that the levels investigated are related to isolated vanadium, and therefore the vanadium acceptor level. Based on the DLTS measurements and secondary ion mass spectroscopy data, the maximum solubility of vanadium in SiC was determined to be 3.0×1017 cm−3. At these incorporation limits and with the depth of the level, the vanadium acceptor level could be used in the creation of semi-insulating silicon carbide. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.115640

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5

Digitale Medien

The effect of Al on Ga desorption during gas source-molecular beam epitaxial growth of AlGaN (1998)

Jenny, J. R. ; Van Nostrand, J. E.

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 72 (1998), S. 85-87

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: In this letter, we report on the impact aluminum has on gallium desorption kinetics in AlGaN alloys grown by gas source-molecular beam epitaxy. Aluminum is found to preferentially incorporate into the AlGaN films over the range of fluxes and temperatures investigated [0.05≤Ji(Ga)≤0.5 ML/s; 0.1≤Ji(Al)≤0.2 ML/s; 700 °C≤Ts≤775 °C]. As a result, Ga is not observed to incorporate into the film until the NH3 flux exceeds that required to grow stoichiometric AlN. This preferential incorporation stems from two facts: (a) Al has an ammonia cracking efficiency ∼2.5 times greater than that of Ga, and (b) Al participates in a Al-for-Ga exchange. As a result of these factors and under NH3 limited growth conditions, the aluminum mole fraction in a layer can be controlled by changing the incident NH3 flux. © 1998 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.120652

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