Andreev reflection and strongly enhanced magnetoresistance oscillations inGaxIn1−xAs∕InPheterostructures with superconducting contacts

Abstract

We study the magnetotransport in small hybrid junctions formed by high-mobility ${\mathrm{Ga}}_{x}{\mathrm{In}}_{1\ensuremath{-}x}\mathrm{As}∕\mathrm{In}\mathrm{P}$ heterostructures coupled to superconducting (S) and normal metal (N) terminals. Highly transmissive superconducting contacts to a two-dimensional electron gas (2DEG) located in a ${\mathrm{Ga}}_{x}{\mathrm{In}}_{1\ensuremath{-}x}\mathrm{As}∕\mathrm{In}\mathrm{P}$ heterostructure are realized by using a $\mathrm{Au}∕\mathrm{Nb}\mathrm{N}$ layer system. The magnetoresistance of the S/2DEG/N structures is studied as a function of dc bias current and temperature. At bias currents below a critical value, the resistance of the S/2DEG/N structures develops a strong oscillatory dependence on the magnetic field, with an amplitude of the oscillations considerably larger than that of the reference N/2DEG/N structures. The experimental results are qualitatively explained by taking into account Andreev reflection in high magnetic fields.