Andreev reflection in engineered Al/Si/InGaAs(001) junctions

Complete suppression of the native n-type Schottky barrier is demonstrated in Al/InGaAs(001) junctions grown by molecular-beam-epitaxy. This result was achieved by the insertion of Si bilayers at the metal-semiconductor interface allowing the realization of truly Ohmic non-alloyed contacts in lowdoped and low-In content InGaAs/Si/Al junctions. It is shown that this technique is ideally suited for the fabrication of high-transparency superconductorsemiconductor junctions. To this end magnetotransport characterization of Al/Si/InGaAs low-n-doped single junctions below the Al critical temperature is presented. Our measurements show Andreev-reflection dominated transport corresponding to junction transparency close to the theoretical limit due to Fermi-velocity mismatch. Typeset using REVTEX a)Also with Università di Trieste, Trieste, Italy.