  We present our recent electronic transport results in top-gated InAs/GaSb
quantum well hybrid structures with superconducting Ta electrodes. We show that
the transport across the InAs-Ta junction depends largely on the interfacial
transparency, exhibiting distinct zero-bias behavior. For a relatively
resistive interface a broad conductance peak is observed at zero bias. When a
transparent InAs-Ta interface is achieved, a zero-bias conductance dip appears
with two coherent-peak-like features forming at bias voltages corresponding to
the superconducting gap of Ta. The conductance spectra of the transparent
InAs-Ta junction at different gate voltages can be fit well using the standard
Blonder-Tinkham-Klapwijk theory.
