Scaling magnetoresistance induced by superconducting contacts in n-type GaAs

A low-temperature (T<4.2 K) transport study of n-type doped (≃${10}^{19}$ ${\mathrm{cm}}^{\mathrm{-}3}$) bulk GaAs reveals an enhancement of the electrical resistance, ΔR/R≃${10}^{\mathrm{-}3}$, below a critical temperature, ${\mathit{T}}_{\mathit{c}}$=3.4 K, at low magnetic fields, B<30 mT, when superconducting In point contacts are used as the current and voltage probes. The resistance correction is shown to be a homogeneous function of the magnetic field, B, and the reduced temperature, τ=(${\mathit{T}}_{\mathit{c}}$-T)/${\mathit{T}}_{\mathit{c}}$, as [ΔR(T,B)/R${]}_{\mathit{s}}$=A${\mathrm{\tau }}^{\mathrm{\kappa }}$f(B/${\mathrm{\tau }}^{\mathrm{\beta }}$) with κ=1.00±0.25, and β=1.00±0.33, in the vicinity of the critical point. The effect is attributed to proximity superconductivity in GaAs resulting from the use of superconducting point contacts.