Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 21: Superconductivity: Poster Session

TT 21.5: Poster

Monday, March 16, 2015, 15:00–18:00, Poster B

Superconducting NbN single-photon detectors on GaAs with an AlN buffer layer — •Ekkehart Schmidt, Michael Merker, Konstantin Ilin, and Michael Siegel — Institut für Mikro- und Nanoelektronische Systeme (IMS), Karlsruher Institut für Technologie, Hertzstrasse 16, 76187 Karlsruhe, Deutschland

GaAs is the material of choice for photonic integrated circuits. It allows the monolithic integration of single-photon sources like quantum dots, waveguide based optical circuits and detectors like superconducting nanowire single-photon detectors (SNSPDs) onto one chip. The growth of high quality NbN films on GaAs is challenging, due to natural occurring surface oxides and the large lattice mismatch of about 27%. In this work, we try to overcome these problems by the introduction of a 10 nm AlN buffer layer. Due to the buffer layer, the critical temperature of 6 nm thick NbN films was increased by about 1.5 K. Furthermore, the critical current density at 4.2 K of NbN flim deposited onto GaAs with AlN buffer is 50% higher than of NbN film deposited directly onto GaAs substrate. We successfully fabricated NbN SNSPDs on GaAs with a AlN buffer layer. SNSPDs were patterned using electron-beam lithography and reactive-ion etching techniques. Results on the study of detection efficiency and jitter of a NbN SNSPD on GaAs, with and without AlN buffer layer will be presented and discussed.