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  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    Differential photoreflectance from a high-mobility and highly luminescent two-dimensional electron gas (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2322-2325 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a differential modulation technique which is effective in extracting the photoreflectance from GaAs/AlxGa1−xAs samples exhibiting excessive room-temperature photoluminescence. Using the technique, we obtain the photoreflectance from the triangular potential-well region of a high-electron-mobility transistor. Surprisingly, the signal from the potential well can be extracted from underneath two layers of heavily doped material, making differential photoreflectance useful in detection of two-dimensional electron gas in high-electron-mobility transistors cladded with doped protective GaAs caps which usually obliterate the PR from the buried interfaces. We isolate absorptionlike photoreflectance peaks at 1.447 and 1.472 eV and show that their energies and the ratio of their amplitudes agree with the 2DEG theory for asymmetric triangular potential well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349427
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  • 3
    Electronic Resource
    Electronic Resource
    Study of deposition dependent characteristics of gold on n-GaAs by photoreflectance spectroscopy (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 910-916 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We used the noncontact electric field modulation technique of photoreflectance to study the effect of gold on GaAs grown by two different metalization methods. A semitransparent 7 nm gold overlayer was grown on low doped n-GaAs (2×1016 cm−3) using metalization by evaporation and by sputtering. Our experimental results indicate that the photoreflectance lineshape depends on the metalization method in a characteristic way. We present evidence of a previously unreported modulation mechanism in photoreflectance. We employed simulation of photoreflectance lineshape based on a multilayer model to reproduce characteristic features of experimental lineshapes. For sputtered Au/GaAs samples the best simulated lineshape was obtained through an unusual modulation, which is based on a strongly pined surface electric field. This produced a lineshape somewhat similar to a third derivative functional form with severely suppressed Franz–Keldysh oscillations (FKO). Simulation with the same set of parameters and a parallel field modulation restored FKO and reproduced the experimental lineshape of the evaporated Au/GaAs. The parallel field modulation spontaneously reproduced the below–band-gap feature, which is often observed in electromodulation spectroscopy. We believe the change in FKO is correlated with the density of interface states as they influence the extent of Fermi-level pinning. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364175
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  • 4
    Electronic Resource
    Electronic Resource
    Differential photoreflectance from modulation-doped heterojunctions (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 948-950 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a new photoreflectance (PR) technique for studies of layered electronic materials. Using the technique, we isolate the reflected signal from buried interfaces and extract the signature from the two-dimensional electron gas in high electron mobility transistor. We compare the results from the technique with conventional PR measurements performed on sequentially etched samples. The results indicate that the new technique picks out the PR from buried interfaces and provides data on the in situ electric fields at the interfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104487
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  • 5
    Electronic Resource
    Electronic Resource
    Electroreflectance-photoreflectance technique for studies of built-in electric field in layered materials (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 527-529 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We use a new modulation technique to investigate photoreflectance from layered electronic materials. The technique can be used to determine the direction of the electric field, and separate the effects of electric field modulation from extraneous modulations due to laser generated charge carriers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109994
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Differential photoreflectance from δ-doped structures and GaAs/n-GaAs interfaces (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 677-679 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using a differential modulation technique we suppress the perturbation of the surface electric field of the sample and extract photoreflectance from buried interfaces. The resulting signals show combinations of a low-field GaAs signature and a high-field oscillatory signal which suggest existence of an ∼30 meV potential offset at the highly doped GaAs/n-GaAs interfaces. The offset is present at both, δ-doped interfaces and simple doped interfaces. For low differential modulation intensities, we observe a signal which could be attributed to two-dimensional electron gas in δ-doped samples, however, the signal cannot be easily differentiated from low-field Franz–Keldysh oscillations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105362
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