An anomalous positive magnetoresistance is observed in layers of GaAs and GaAs&3b0,,, doped with Ge (p-type conductivity) which is found t o be governed by quantum effects. In the analysis the degeneracy of the valence band is considered and the contribution extracted corresponding t o the total moment, I = 0, of the pair of particles. The wave function phase relaxation time is found. The origin of the magnetoresista,nce which cannot be described by the theoretical expression for I = 0 is discussed. B nneHKax GaAs Theoretical BackgroundThe theory of weak localization with account of strong spin-orbit coupling in cubic p-type semiconductors with fourfold degenerate valence band a t k = 0 has explained qualitatively [ 11 the experimentally observed anomalous positive magnetoresistance (APMR) in such systems and its sign reversal a t removing the degeneracy by, for example, applying strain to a cryst,al [2].The states in the degenerabe va-lence band correspond to the momentum 312 and the momentum projections m = 312, 112, -112, -312. I n accordance with theory [l] the probability of wave function interference in this case may be represented as a sum of four terms corresponding t o the total momentum of a pair of particles I = 0, 1, 2, and 3, and the magnetic field dependence of the conductivity is given by A a ( H ) = -;-Aar=s -Aor=z + Aar,i -f Aar=o .(1)Here the last term is determinated only by the wave function phase relaxation timet, :where D is the diffusion constant, the function f 3 ( x ) has been introduced by Kawabata [3]. The other terms in (1) depend on various, but not calculated, combinations of the times z , and z , , (tso being the spin-orbit scattering time). Because of the strong spin-orbit coupling in the cubic p-type semiconductors [4] zso x t, i.e. SU-194021 Leningrad, USSR.
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