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Publications (4)5.28 Total impact

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    ABSTRACT: We report measurements of the diagonal component of the thermoelectric power in a superlattice and a heterojunction of GaAs and GaAlAs. The qualitative variation of the thermopower with magnetic field is in agreement with both theoretical studies and previous experimental measurements. Quantitatively, the behaviour of the superlattice agrees with calculations for an ideal two-dimensional system, but both the magnitude and temperature dependence of the thermopower in the heterojunctions cannot be explained by existing theories.
    Solid State Communications 02/1986; 57(6):381–384. · 1.53 Impact Factor
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    ABSTRACT: The diagonal component of the thermoelectric power in GaInAsInP, GaInAsAlInAs and GaAsGaAlAs heterojunctions and a GaAsGaAlAs superlattice has been studied as a function of magnetic field and temperature. In high magnetic fields, the thermopower shows oscillations proportional to the resistivity oscillations, including features due to spin splittings and the occupation of two electric subbands. The peak values of the thermopower in the GaAsGaAlAs superlattice are almost independent of temperature and close to the theoretical predictions. In contrast, the peak thermopowers measured in the heterojunctions are lower than predicted by factors of between 2 and 50, and decrease with increasing temperature.
    Surface Science Letters 01/1986; 170.
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    ABSTRACT: Low‐temperature photoluminescence (PL) measurements have been performed on several molecular‐beam epitaxial high‐quality GaAs layers showing varied electrical characteristics (nominally undoped and intentionally doped n or p type). This work is carried out with a view to investigate the influence of the centers responsible for the defect–bound‐exciton emissions (d,x) on the electrical properties of the layers. After a systematic study of the luminescence properties of the d,x emissions as a function of the electrical nature (doped n or p type), residual p doping level, PL excitation intensity, and sample temperature, we came to the following conclusion: In addition to the prominent residual carbon acceptors, at least a part of p conduction in nominally undoped p‐type layers could come from the centers responsible for the d,x emission at 1.5109±0.0003 eV. This suggestion is tentatively ascertained by detecting an acceptor emission at ∼1.496±0.001 eV, shallower than the carbon acceptor about 3 meV. All these results in addition to those related to the detection of deeper acceptors in the spectral range 1.46–1.49 eV are presented and discussed.
    Journal of Applied Physics 02/1985; · 2.21 Impact Factor
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    ABSTRACT: The evolution of fractionally quantised states has been studied in a GaAsGaAlAs heterojunction as a function of electron concentration at very low temperatures using magnetic fields up to 16T. The electron concentration was progressively increased by the use of the persistent photoconductivity effect, and it was found that the fractionally quantised states at occupancies of became much more pronounced. The state gave only a weak resistivity minimum and no Hall plateau at the highest concentration studied (4.6×1011cm−2), in contrast to the state, for which a wide Hall plateau and a deep resistivity minimum were observed.
    Solid State Communications 01/1985; · 1.53 Impact Factor