We report on the successful fabrication of low leakage aluminium superconducting tunnel junctions with very homogeneous and transparent insulating barriers. The junctions were tested in an adiabatic demagnetisation refrigerator with a base temperature of 35 mK. The normal resistance of the junctions is equal to ~7 uohm cm2 with leakage currents in the bias voltage domain as low as 100 fA/um2. Optical single photon counting experiments show a very high responsivity with charge amplification factors in excess of 100. The total resolving power (including electronic noise) for 500 nm photons is equal to 13 compared to a theoretical tunnel limited value of 34. The current devices are found to be limited spectroscopically by spatial inhomogeneities in the detectors response
@article{arxiv.cond-mat/0407318,
title = {Optical photon detection in Al Superconducting Tunnel Junctions},
author = {G. Brammertz and A. Peacock and P. Verhoeve and D. Martin and R. Venn},
journal= {arXiv preprint arXiv:cond-mat/0407318},
year = {2009}
}