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Magnetoresistance in low-temperature grown molecular-beam epitaxial GaAs

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5 Author(s)
Betko, J. ; Institute of Electrical Engineering, Slovak Academy of Sciences, SK-84239 Bratislava, Slovakia ; Morvic, M. ; Novak, J. ; Forster, A.
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Conductivity, Hall effect as well as “physical” and “geometrical” magnetoresistances were measured at 290–440 K in molecular-beam epitaxial GaAs layers grown at 200–400 °C. The experimental data were analyzed taking into account the combined band and hopping conductance regime. Positive hopping magnetoresistance parameters (Δρ/ρ0B2)h≈10-4T-2 and hopping Hall mobilities lower than 1×10-4m2 V-1 s-1 were determined in the as-grown layers. A transverse-to-longitudinal hopping magnetoresistance ratio of about 2, consistent with hopping transport theories, was obtained. In the annealed layer grown at 200 °C (J200a) the band mobility determined from the geometrical magnetoresitance (GMR) mobility was found to be significantly higher than the band Hall mobility. It is related to a mixed band conductivity regime with the hole concentration p exceeding the electron one n. The difference between GMR and Hall mobilities decreases with increasing growth temperature as far as a typical single-carrier band conductivity regime (n≫p) is present in the layer grown at 400 °C. In contradiction to the layers grown at higher temperatures, the J200a layer showed the opposite (positive) sign of the hopping Hall coefficient as well as the largest hopping magnetoresistance parameter (≈3×10-2T-2). © 1999 American Institute of Physics.  

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Journal of Applied Physics  (Volume:86 ,  Issue: 11 )