Andreev Reflection in a Superconducting Light-Emitting Diode.

We experimentally demonstrate Cooper-pair injection into a superconducting light-emitting diode by observing Andreev reflection at the superconductor-semiconductor interface, overcoming the contradicting requirements of an electrically transparent interface and radiative recombination efficiency. The device exhibits electroluminescence enhancement at the quasi-Fermi energy at temperatures below Tc. The theoretically predicted conductance and electroluminescence spectra based on Cooper-pair injection into the semiconductor correspond well to our experimental results. Our findings pave the way for practical superconductor-semiconductor quantum light sources.