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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of InGaSb by photoreflectance spectroscopy (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1175-1178 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance (PR), a contactless form of electromodulation, is used in a study of the In1−xGaxSb alloy series. The samples consist of epilayers of In1−xGaxSb (0.780≤x≤0.900) grown by molecular beam epitaxy onto (100) GaSb substrates, resulting in percent mismatches between the substrate and layers ranging from 0.62% to 1.36%. These relatively small mismatches result in the epilayers being under a considerable amount of compressive stress. The effects of this strain field on the optical properties are seen through shifts and splittings of the PR spectra. These are exploited to determine the relative changes in the electronic band structure of the material. It is found that the shifting of the heavy-hole and spin orbit split off valence bands correspond well with the theory, while the light hole bands do not. A possible explanation for this is given. Results of a study of the compositional dependence of the In1−xGaxSb energy gaps are also presented. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1429764
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  • 2
    Electronic Resource
    Electronic Resource
    Photoreflectance study of ion beam synthesized β-FeSi2 (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 1219-1223 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photoreflectance spectra of ion beam synthesized β-FeSi2 reveals a direct gap at 0.815 eV and are shown to agree with the band gap value obtained by photoluminescence once the adjustments for the temperature difference and trap related recombination effects are made. This provides very convincing evidence for intrinsic light emission from ion beam synthesized β-FeSi2. Furthermore, we propose a simple model that helps to clarify the variety of inconsistent results obtained by optical absorption measurements. When the results of photoluminescence and photoreflectance are inserted into this model, we obtain good agreement with our measured optical absorption results. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1428792
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  • 3
    Electronic Resource
    Electronic Resource
    Raman investigation of ion beam synthesized β-FeSi2 (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 965-972 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Raman spectra of ion beam synthesized (IBS) β-FeSi2 are investigated and evidence for the presence of a net tensile stress is presented. Possible origins of the observed stress are suggested and a simple model is proposed in order to calculate a value of the observed stress. A correlation between the tensile stress, the nature of the band gap, and the resulting light emitting properties of IBS β-FeSi2 is suggested. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1326473
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  • 4
    Electronic Resource
    Electronic Resource
    Pressure concentration isotherms of thin films of the palladium-hydrogen system as modified by film thickness, hydrogen cycling, and stress (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 5236-5239 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe the results of a novel adaptation of the volumetric technique to measurement of the pressure concentration isotherms for thin films of the palladium-hydrogen system. The isotherm shapes are comparable to bulk being steep in the alpha and beta phases and flat in the mixed phase region. However, it is noted that the concentration onset of the beta phase is smaller than bulk and drops markedly for thicknesses less than 670 A(ring). Comparison is made with quartz crystal microbalance results. We find a thickness dependence to the number of absorption-desorption cycles required to obtain reproducible isotherms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335262
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  • 5
    Electronic Resource
    Electronic Resource
    Photoreflectance studies of silicon films on sapphire (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 3303-3308 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the results from the photoreflectance (PR) analysis of a set of molecular-beam epitaxially grown silicon on sapphire films whose thicknesses ranged from 6 to 4000 nm. The strain undergone by the silicon films due to lattice mismatch at the silicon sapphire interface and to the difference in the thermal expansion coefficient of the two materials was investigated. To this purpose the position of the 3.4-eV PR structure was monitored with bulk silicon as a standard. A shift of this structure toward lower energies was observed in the thinnest films. A drastic increase in elasticity is observed as the film thickness varies from 550 to 700 nm. This fact can be correlated with transmission electron microscope observations of the predominant defects in the films. Special attention was also devoted to the effects of native oxide on the films, that appeared to cause a shift of the 3.4 eV structure toward higher energies. This shift suggests that the native oxide layer is exerting a compressive strain on the silicon films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348552
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  • 6
    Electronic Resource
    Electronic Resource
    Correlation between the photoreflectance response at E1 and carrier concentration in n- and p-GaAs (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2525-2531 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated the photoreflectance (PR) response of metalorganic chemical vapor deposition-grown n- and p-type GaAs at the higher-energy transition E1(≈2.9 eV). The doping level range of interest was 2×1016–4×1018 cm−3 for Si:GaAs and 6×1016– 1×1019 cm−3 for Zn:GaAs. Both the position and the broadening parameter, Γ1, of the E1 transition within the doping concentration range were investigated. The evaluation of Γ1's, based on the curve fitting of the PR response and the Kramers–Kronig analyzed data reveal a nearly linear relation between Γ1 and the logarithm of the carrier concentration. This observation has the potential application for contactless determination of carrier concentration in moderate and heavily doped nanoscale films. Secondary-ion mass spectroscopy measurements show that there is relatively large compensation in Si:GaAs samples, but it does not correlate with the broadening of the E1 structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348691
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  • 7
    Electronic Resource
    Electronic Resource
    Diamond growth in turbulent oxygen-acetylene flames (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 7561-7571 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Turbulent premixed oxygen-acetylene flames have been used to synthesize polycrystalline diamond films on molybdenum substrates at temperatures ranging from 500 to 1300 °C and facetted single crystals on mm-sized natural diamond substrates at temperatures of 1200–1300 °C. Turbulence was achieved by increasing the torch's orifice diameter and/or the flow velocity; the presence of turbulence was confirmed by observations of changes in the flame shape, measurements of the flame's noise spectrum, and calculations of the Reynolds number. The optical emission spectra of several diamond-growing turbulent flames were also compared to the spectra of laminar flames. The variation in diamond quality with temperature and oxygen acetylene flow ratio was studied with one or more of the following techniques: Raman spectroscopy, scanning and transmission electron microscopy, infrared spectroscopy, and photoluminescence spectroscopy. Crystals grown on molybdenum at temperatures of 600–1100 °C were observed to be transparent, and under the proper conditions the quality of diamond grown epitaxially in a turbulent flame equals that of natural type-IIa diamond. Although this enhanced quality has only been observed for fairly lean flames, the growth rate for type-IIa quality diamonds can still exceed 35 μm/h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354982
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  • 8
    Electronic Resource
    Electronic Resource
    Photoreflectance optimization: A comparison between monochromator and glass filters for photoluminescence and laser light elimination (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2327-2330 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article evaluates a photoreflectance apparatus in which unwanted photoluminescence and laser light are separated from the signal by a monochromator placed in front of the detector as compared to separation by the more commonly used glass filters. We present results from the application of both techniques to the study of the 3.4- and 4.3-eV structures in both bulk silicon and silicon films on sapphire, the 1.4-eV structure in GaAs, and the 1.8-eV structure of Al0.33Ga0.77As. The replacement of glass filters with a second monochromator, in addition to allowing a better rejection of spurious light, extends the range of wavelengths in which a satisfactory photoreflectance signal can be obtained and permits observation of a signal closer to the modulating laser line. On the other hand the use of glass filters can be preferable for high laser power, for weak signals in regions of low grating efficiency, or merely for economical reasons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141359
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  • 9
    Electronic Resource
    Electronic Resource
    Front contact electroreflectance: An alternative technique for semiconductor optical studies (1991)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 1027-1030 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An alternative form of application of an electric field to semiconductors so as to provide electroreflectance modulation is presented. Two metallic contacts, a large ring-shaped one enclosing a small transparent one, are deposited on the specimen surface and connected to the two leads of a signal generator. Results from a highly doped n-type silicon bulk and from an undoped 4000 nm silicon film on sapphire demonstrate that this technique yields spectra equivalent to traditionally performed electroreflectance or photoreflectance. We also show that electroreflectance response can be obtained with a current generator connected across a single metal contact.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142053
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  • 10
    Electronic Resource
    Electronic Resource
    Carrier concentration determination by photoreflectance at E1 in thin film, highly doped GaAs (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1218-1220 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance (PR) response at the E1 (2.9 eV) transition of GaAs doped with Si, Zn, and Be was investigated within the range of 1.5×1015 to 2×1019 cm−3. Growth technique was either metalorganic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). We find that Γ1, the broadening parameter of the E1 structure increases linearly with the logarithm of the measured carrier concentration over the range of ≈1×1017 to ≈1×1019 cm−3. A slope of 56±5 meV/decade describes all Si:GaAs samples independent of growth technique. For p-GaAs, the slope is 30±3 meV/decade over a comparable range and is independent of doping element as well as growth technique. This linear relation could be employed as a contactless means of determining carrier concentration. The energy position of E1 shows no significant shift in the above range. We believe that the broadening is a result of the doping produced, electric field within the depletion region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105508
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