Silicon Devices Optimised for Avalanche Multiplication

We give an overview about new silicon devices for particle detectors that exploit the avalanche phenomenon of a reverse-biased pn junction to give an internal moderate gain. These new devices, the Low Gain Avalanche Detectors (LGAD), offer proportional response and good efficiency as the PiN diodes, and also a higher signal, while the noise in not increased significantly. In this paper we present the results of an extensive characterization campaign. The LGAD diodes -developed and fabricated at IMB-CNM (Barcelona, Spain)exhibit good electrical characteristics (current stability and high breakdown) before and after irradiation. Studies carried out with red laser TCT have shown that both front and back surface (before irradiation) are very uniform. The devices also offer excellent performances before irradiation in terms of charge collection, with a gain of ~10. Nevertheless, a severe decrease of the gain has been observed after neutron or proton irradiation at high fluences, so that further studies are ongoing in order to increase their radiation resistance. Timing measurements have also shown that the LGAD detectors are ideal candidates for the realization of silicon detectors with very good space and time resolution, for 4-dimensional tracking of charged particles. Such devices could be applied as time-of-flight detectors for physics experiments, and as particle counters for dosimetry. The 23rd International Workshop on Vertex Detectors 15-19 September 2014 Macha Lake, The Czech Republic P o S ( V e r t e x 2 0 1 4 ) 0 3 1 P o S ( V e r t e x 2 0 1 4 ) 0 3 1 P o S ( V e r t e x 2 0 1 4 ) 0 3 1 Devices Optimised for Avalanche Multiplication Greco Virginia et al. G Author(s)