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  • 1
    Electronic Resource
    Electronic Resource
    Application of Vapor Phase Chromatography to Mass Spectrometer Analysis (1956)
    s.l. : American Chemical Society
    Analytical chemistry 28 (1956), S. 979-983 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac60114a015
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  • 2
    Electronic Resource
    Electronic Resource
    Thermal decomposition of lithium perchlorate. II. Chloride catalysis (1974)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 78 (1974), S. 776-779 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100601a003
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  • 3
    Electronic Resource
    Electronic Resource
    Deep levels in undoped horizontal Bridgman GaAs by Fourier transform photoconductivity and Hall effect (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 246-251 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Deep levels between 0.1 and 1.0 eV in semi-insulating and high resistivity undoped horizontal Bridgman GaAs have been studied by temperature-dependent Hall effect (TDH) and Fourier transform photoconductivity (FTPC). Activation energies at 0.77, 0.426, and 0.15 eV have been observed by TDH. Photoionization thresholds at 1.0, 0.8, 0.56, 0.44, and 0.25 are reported. The photoconductivity thresholds at 0.56 and 0.25 eV are reported for the first time. New features in the 0.44 eV threshold suggest that the defect responsible for this level has a small lattice relaxation and Frank–Condon shift. Possible associations of the FTPC and TDH energies with the deep-level transient spectroscopy levels EL2, EL3, and EL6 are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350750
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  • 4
    Electronic Resource
    Electronic Resource
    Fermi level control and deep levels in semi-insulating 4H–SiC (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 5040-5044 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature dependent Hall effect, optical admittance spectroscopy, and optical absorption measurements of semi-insulating bulk 4H–SiC are reported. Both intentionally vanadium doped material and commercial grade semi-insulating material were investigated. The carrier concentration versus inverse temperature results from Hall effect measurements up to 1000 K indicated the samples were dominated by one of two deep levels near midgap. In addition to the deep donor level of substitutional vanadium, Ec−1.6 eV, we observed another level at Ec−1.1 eV in some samples, indicating that levels other than the vanadium donor can pin the Fermi level in semi-insulating SiC. Optical admittance measurements on the semi-insulating material indicate the presence of levels at Ec−1.73 and 1.18 eV that were previously observed in conducting samples with this technique and we attribute these levels to the same defects producing the 1.1 and 1.6 eV levels seen by Hall effect. Secondary ion mass spectroscopy measurements of dopant and impurity concentrations are reported. Even though vanadium is present in all of these samples, along with other impurities we are at present unable to definitively identify the 1.1 eV level. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371476
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  • 5
    Electronic Resource
    Electronic Resource
    Shallow and deep levels in n-type 4H-SiC (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7726-7730 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nitrogen levels in 4H-SiC have been determined using thermal admittance spectroscopy. The values of Ec−0.053 eV for nitrogen at the hexagonal site and Ec−0.10 eV for nitrogen at the quasicubic site agree with those reported using other techniques. The deep levels in 4H-SiC were studied using optical admittance spectroscopy. The optical admittance spectrum showed, besides the conductance peak corresponding to band to band transitions, four other conductance peaks. These peaks correspond to photoexcitation of carriers from the defect levels to the conduction band. It is inferred from a comparison with 6H-SiC that the conductance peak b4 is due to excitation of electrons from the vanadium donor at Ec−1.73 eV. The photoconductance build up transients of the Ec−1.73 eV level are described fully by one exponential term. This suggests that only one center contributed to the observed conductance. The decay kinetics of persistent photoconductance due to the Ec−1.73 eV level follow the stretched exponential form. The potential barrier against recapture of photoexcited carriers was determined to be 18 meV for the vanadium donor level in 4H-SiC. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362376
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  • 6
    Electronic Resource
    Electronic Resource
    Shallow levels in n-type 6H-silicon carbide as determined by admittance spectroscopy (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 3472-3476 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Admittance spectroscopy has been used to study shallow levels in n-type 6H-SiC single crystals. A total of eight unintentionally doped n-type samples obtained from three different sources were used in this study. Two of the samples were grown by the Lely method, while the others were grown by physical vapor transport. Two electron traps at EC−0.04 eV and EC−0.03 eV were detected in the more heavily n-type (ND−NA=1018 cm−3) samples. These defects may be due to contaminants other than nitrogen. A defect level at EC−0.08 eV as detected in a sample with ND−NA=8.9×1017 cm−3. This level is associated with nitrogen at the hexagonal site (h). An electron trap at EC−0.11 eV was detected and is associated with nitrogen at the quasicubic sites (k1k2). This level was observed only in the lightly n-type samples (ND−NA=4.7 ×1015–6.4×1017 cm−3).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356108
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  • 7
    Electronic Resource
    Electronic Resource
    Determination of the valence-band discontinuity in Be-doped GaAs/Al0.3Ga0.7As multiple-quantum wells using admittance spectroscopy (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1010-1013 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Admittance spectroscopy has been used to determine the value of the valence-band discontinuity in a p-type GaAs/Al0.3Ga0.7As multiple-quantum-well system. The structures were multiple quantum wells grown by molecular-beam epitaxy on semi-insulating GaAs substrates. Three Be-doped (p-type) GaAs wells, 30, 35, and 40 A(ring) wide, were used in these measurements. The barriers were undoped. Based on our measurements and a Fermi-level determination from an 8×8 envelope function approximation calculation of the valence electronic structure of the GaAs/AlGaAs system, the valence-band discontinuity, ΔEv, was found to be 0.165 eV. Using established relations, the band-gap difference in the GaAs/AlGaAs system ΔEg for xAl=0.3 was calculated to be 0.429 eV, which, together with the valence-band offset determined in this work, gives the ratio of the conduction–to–valence-band offsets as 60:40. These values are in excellent agreement with those determined by capacitance-voltage profiling, thus confirming the utility of the admittance spectroscopic technique for determining the band discontinuities in band-gap-engineered materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356507
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  • 8
    Electronic Resource
    Electronic Resource
    Reply to "Comment on ‘Temperature dependence of the barrier height of metal-semiconductor contacts on 6H-SiC' '' (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6572-6573 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We reply to the comment by Fröjdh and Petersson concerning the measurements of the barrier heights of Schottky diodes on 6H-SiC. We present the argument that the temperature range over which Fröjdh and Petersson present data does not allow accurate comparison with our results. The problem of interaction of deep levels in the capacitance-voltage measurements is refuted by deep-level transient spectroscopy data. We conclude that our data are accurate and our methods reliable. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363644
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  • 9
    Electronic Resource
    Electronic Resource
    Temperature dependence of the barrier height of metal-semiconductor contacts on 6H-SiC (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 301-304 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have examined the temperature dependence of the barrier height of Al, Ag, Au, and W metal-semiconductor contacts on n-type 6H-SiC, and Al and Ag metal-semiconductor contacts on p-type 6H-SiC. The barrier height was determined from the reverse biased capacitance-voltage characteristics of the contacts at temperatures ranging from 300 to 670 K. The measurements were made at 1 MHz. These measurements were compared to the behavior predicted by standard models. All the diodes displayed a negative temperature dependence on n-type SiC, and a positive temperature dependence on p-type SiC. The temperature coefficient is related to the electronegativity of the metal by linear expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360944
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  • 10
    Electronic Resource
    Electronic Resource
    Optical admittance studies of vanadium donor level in high-resistivity p-type 6H-SiC (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 253-258 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The vanadium donor level in high-resistivity p-type 6H-SiC has been studied using optical admittance spectroscopy. Besides the conductance peak due to the band to band transitions, there are three conductance peaks in the spectra of most of the samples. These peaks correspond to photoexcitation of electrons from the valence band to the defect levels. The conductance peak due to the vanadium donor [V4+(3d1)] level at Ev+1.55 eV is identified. The build up of the photoconductance at this peak was studied and it was found that the conductance transients are completely described by a sum of two exponential expressions. The relevant parameters, α1, α2, Gmax(1) and Gmax(2), were determined as functions of temperature. The persistent photoconductance (PPC) due to this defect was also studied. The decay kinetics of the PPC follow the stretched exponential form. The potential barrier against recapture of carriers was determined to be 220 meV for the vanadium donor level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360938
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