Signature of Superconducting Density of States in Luminescence Spectra of InAs Quantum Dots

We report the observation of signature of superconducting density of states (DOS) in the luminescence spectra from InAs quantum dots (QDs) for the first time. Cooper pairs penetrate from a niobium (Nb) superconductor to an adjacent n-type InGa(Al)As heterostructure with the proximity effect. The luminescence is rate-limited by the population of minority holes injected with photo-excitation. The QD luminescence intensity was enhanced more than 3 times below the superconducting critical temperature. This advances a step toward realizing the superconductor-based QD light-emitting diode (SQLED) that we proposed previously for generating entangled photon pairs (EPPs).