Superconducting Nanowire Single-Photon Detectors based on TaN Thin Films
Mathematisch-Naturwissenschaftliche Fakult, Adrian Aeschbacher
Superconducting Nanowire Single Photon Detectors (SNSPD) are very fast, low noise devices, that detect single photons over a broad spectral range with practical quantum efficiency. The quantum efficiency drops at a certain deposited energy abruptly, the so called cutoff energy or the corresponding cutoff wavelength. The most common material to fabricate these nanowires is niobium nitride (NbN). A promising material, that has not been used for this purpose before is tantalum nitride (TaN). Many material properties of TaN and NbN are similar, but TaN has a smaller energy gap. This should make the device more sensitive to photons with lower energies. In this thesis, SNSPDs made of NbN and TaN were characterized, the quantum efficiencies were measured and the cutoff criteria were determined and compared. With the use of TaN the cutoff wavelength could be increased significantly. Measurements of quantum efficiency and dark-count rates at several temperatures and operation conditions are presented and discussed. Furthermore, the cutoff criteria are determined and compared between the materials mentioned as well as the experimental results are compared to the theoretical predictions of the detection model.
•Jan 1, 2011•0 citations