Andreev reflection in engineered Al/Si/InxGa1-xAs(001) junctions

Complete suppression of the native n-type Schottky barrier is demonstrated in Al/InxGa1-xAs(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 low-doped and low-In-content InxGa1-xAs/Si/Al junctions. It is shown that this technique is ideally suited to the fabrication of high-transparency superconductor-semiconductor junctions. To this end, magnetotransport characterization of Al/Si/InxGa1-xAs 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.