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  • 1
    Electronic Resource
    Electronic Resource
    Photoreflectance, absorption, and nuclear resonance reaction studies of AlxGa1−x As grown by molecular-beam epitaxy (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 5447-5453 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photoreflectance (PR) spectra of bulk AlxGa1−xAs alloys with x≤0.45 were studied. The observed line shapes from different samples suggest that the PR technique is very sensitive to the material quality, surface condition, and the background impurities. The energy gap derived from the PR spectra compared well to that obtained from the absorption spectra. The relationship between the energy gap and the Al mole fraction value x was established through the nuclear resonance reaction analysis. The electric field near the surface was calculated from the periodicity of Franz–Keldysh oscillations observed in many of the samples. From our analysis, we believe that the number of oscillations shown in PR spectra corresponds to sample quality, in general. We also believe that the low-field-like line shape is mainly caused by the fluctuation of Al distribution along the growth direction. An additional feature related to the impurity transition was also observed in the spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340366
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  • 2
    Electronic Resource
    Electronic Resource
    Investigation of GaAs/(Al,Ga)As multiple quantum wells by photoreflectance (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 145-151 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Room-temperature photoreflectance has been used to investigate a series of GaAs/(Al,Ga)As multiple quantum-well structures. In addition to the allowed (as high as n=5) and symmetry forbidden transitions, we have observed transitions involving the so-called "unconfined'' states, which have received less attention so far. We have examined these transitions more carefully by studying a low barrier multiple quantum-well structure and observed transitions as far as 200 meV beyond the barrier gap. By using a simple two-band tight-binding model, the energies and matrix elements for these unconfined transitions were calculated and shown to agree with the experimental values determined by fitting the photoreflectance spectra to the theoretical line-shape expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339172
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  • 3
    Electronic Resource
    Electronic Resource
    Electroreflectance studies above the fundamental gap on InxGa1−xAs layers deposited on GaAs (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 266-267 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interband transitions E1 and E1+Δ1 were investigated using the electrolyte electroreflectance technique for various compositions of InxGa1−xAs layers deposited on GaAs by molecular-beam epitaxy. A discrepancy in the results for layers deposited with lattice mismatch and bulk materials was noticed. The results were compared with the predictions of the scaled-virtual-crystal-approximation method for transition energy dependence on composition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336875
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  • 4
    Electronic Resource
    Electronic Resource
    Optical investigation of highly strained InGaAs-GaAs multiple quantum wells (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 3366-3373 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-temperature optical transmission spectra of several InxGa1−xAs/GaAs strained multiple quantum wells (MQWs) with different well widths and In mole fractions have been measured. The excitonic transitions up to 3C-3H are observed. The notation nc-mH(L) is used to indicate the transitions related to the nth conduction and mth valence heavy (light) hole subbands. Steplike structures corresponding to band-to-band transitions are also observed, which are identified as 1C-1L transitions. The calculated transition energies, taking into account both the strain and the quantum well effects, are in good agreement with the measured values. In these calculations the lattice mismatch between the GaAs buffer and the InGaAs/GaAs MQW is taken into account and the valence-band offset Qv is chosen as an adjustable parameter. By fitting the experimental results to our calculations, we conclude that the light holes are in GaAs barrier region (type II MQW) and the valence-band offset Qv is determined to be 0.30. A possible system in which the transition from type I to type II for light holes might be observed is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339299
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of dc bias on electrolyte electroreflectance spectra (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 368-371 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of a constant component of electric field (dc bias) across an electrolyte–semiconductor interface are studied and discussed. The change of bias causes variations in spectral features depending on the type of the semiconducting material and the position of a feature in relation to the interband transition energy. The phenomena are illustrated in experiments carried out on GaAs and HgMnTe. It is experimentally shown that dc bias in conjunction with the electrolyte electroreflectance technique can be used to determine the type of the material, to locate the flat-band potential, and to study the surface states. It has also been shown that dc bias can be used to determine low field conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337655
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  • 6
    Electronic Resource
    Electronic Resource
    Nonalloyed and alloyed low-resistance ohmic contacts with good morphology for GaAs using a graded InGaAs cap layer (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 867-869 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using a thin graded layer of InGaAs starting on GaAs and becoming InAs on the top, low-resistance alloyed and nonalloyed ohmic contacts have been achieved on n+-GaAs epilayers grown by molecular-beam epitaxy on a semi-insulating GaAs substrate. In addition, by a suitable choice of the multilayer ohmic metals and by an optimization of the alloying process, good surface morphology was obtained. The transmission-line model is used to extrapolate contact resistances from measurements on test patterns with multiple gap spacings varying from 1 to 10 μm. The nonalloyed contact resistance is found to be 0.025 Ω mm for a GaAs layer doped to 1×1018 with a 500-A(ring) graded InGaAs layer. Alloying the contact at 475 °C for 60 s produces a contact resistance of 0.019 Ω mm. This represents a substantial improvement over the contact resistances obtained by just using an ungraded cap layer of InAs on GaAs. Assuming that the sheet resistance under the contact is the same as the sheet resistance in the top semiconductor layer (this is not strictly true), the nominal value of the specific contact resistance for the nonalloyed situation is 5.32×10−7 Ω cm2, while for the alloyed case the specific contact resistance is 2.56×10−7 Ω cm2. The metal scheme used for the contact is Ni/Ge/Au/Ti/Au.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343080
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  • 7
    Electronic Resource
    Electronic Resource
    Investigation of GaAs/(Al,Ga)As multiple quantum wells grown on Ge and Si substrates by molecular-beam epitaxy (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 4858-4862 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report photoreflectance studies on GaAs/(Al,Ga)As multiple quantum wells grown on Si and Ge substrates. The sharp spectral features observed from various subband transitions indicate that good epilayer quality can be obtained on nonpolar substrates using suitable growth techniques. The experimental results agree well with calculated values based on the envelope function approximation, when the effect of residual strain resulting from the large difference in thermal expansion between GaAs and Si is taken into account.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339832
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  • 8
    Electronic Resource
    Electronic Resource
    Automatic topographic examination of semiconductors using modulated reflectance (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 268-272 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A modified cell design for studies of electrolyte electroreflectance of solids is reported. A new type of electrolyte cell design for ensuring easy and proper contacts with the surface of the sample wafer is described. The modified system is shown to be suitable for fast and convenient acquisition and display of spectra, or the variation of composition or carrier concentration as a function of position on the sample. Typical results for GaAs:Si and MBE-grown Ga1−xAlxAs/GaAs samples are shown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138342
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  • 9
    Electronic Resource
    Electronic Resource
    Interband transitions in molecular-beam-epitaxial AlxGa1−xAs/GaAs (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 495-498 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interband transition energies for AlxGa1−xAs layers grown by molecular-beam epitaxy (MBE) techniques have been determined using the electrolyte electroreflectance (EER) technique. The observed data fit quadratic relations for E0, E0+Δ0, E1 and E1+Δ1 to describe variations of energy with composition. Although the x values were not accurately known, the internal consistency of the data is excellent. Given a single bowing parameter we show that accurate values of x can be determined. The EER technique can provide x values with an accuracy better than 0.02 and information on changes in x as small as 0.002. It is thus ideally suited for studying MBE materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335652
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  • 10
    Electronic Resource
    Electronic Resource
    Enhanced ballistic transport in InGaAs/InAlAs hot-electron transistors (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 1254-1255 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hot-electron transistors fabricated using a 600-A(ring) InGaAs base and a 500-A(ring) InAlAs barrier have shown a peak ballistic common base current gain of 0.82 at 77 K despite the large injection energies. Reduction of injection energies by lowering the emitter and collector barriers should lead to an even higher ballistic transport ratio due to the reduced Γ-L scattering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98696
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