Mo - Si superconducting nanowire single-photon detectors on GaAs

We report on Mo-Si-based superconducting nanowire single-photon detectors on a gallium arsenide substrate. Mo-Si deposited on a passivated GaAs surface has the same critical temperature as Mo-Si deposited on silicon. The critical temperature decreases slightly on depositing Mo-Si directly on the native oxide of GaAs. Hence, Mo-Si works well as a thin-film superconductor on GaAs. We propose that the amorphous structure of Mo-Si ensures compatibility with the GaAs matrix. Superconducting nanowire single-photon detectors (SNSPDs) are fabricated with Mo-Si on GaAs using a meander-wire design. The SNSPD metrics are very similar to those of devices fabricated with the same procedure on a silicon substrate. We observe a plateau in the response-versus-bias curve, signaling a saturated internal quantum efficiency. The plateau remains even at an elevated temperature, 2.2 K, at a wavelength of 980 nm. We achieve a timing jitter of 50 ps and a recovery time of 29 ns. These results point to the promise of integrating Mo-Si SNSPDs with GaAs photonic circuits.