Electron mobility in compensated GaAs and AlxGa1−xAs

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Abstract
The dependence of electron mobility μ on temperature T in GaAs and AlxGa1−xAs indicates that for compensated material a term having μ∝T−1/2 causes a significant reduction in the mobility measured at high temperatures. The magnitude of the T−1/2 term in mobility, denoted μCA, is found to be linearly proportional to the compensating acceptor concentration over a range of more than two orders of magnitude in samples with no intentional doping where carbon is the major compensating acceptor. Intentional compensation using Ge and Zn is found to have no effect on μCA. Illumination (hν≳EG) has no effect on μCA. Such illumination is demonstrated to significantly reduce the size of space‐charge layers at the n‐i interface. Thus, the T−1/2 mobility is not due to scattering by space‐charge regions as has been previously assumed. The acceptor C, or an associate involving C, is concluded to be the scattering center responsible for μCA. The effect may be due to the short‐range central‐cell potential resulting from the large electronegativity difference between C and the As for which it substitutes in the lattice.