Silicon based photodetection in science: challenges and perspectives

The entire silicon based imaging industry evolved around the concept of charge-coupled devices (CCD) [1] introduced in 1969. In parallel to the development of the CCD technology, in the 1990’s and 2000’s the entire CMOS based microelectronic industry was making huge advances in what the processing technology is concerned. In the early 1990s, huge efforts were first started to take advantage of this highly developed process technology to try to create highly functional single-chip image sensors where low cost, high yield, and the possibility of inclusion of in-pixel intelligence and on-chip signal processing – an electronic camera-on-a-chip [2] – was the driving factor. Reaching the 2010’s, instead of having CMOS processes that deliver highly functional logic circuitry with quite bad front-end photosensing performance, most foundries started investing in the development of photosensitivity enhanced processes still capable of delivering a quite acceptable CMOS functionality. Near single photon counting with picosecond time resolution has been one of the main breakthroughs of the last couple of years. This was achieved in the form of single-photon counting avalanche diodes (SPADs) [3] and Silicon Photomultipliers (SiPMs) [4]. They are realized nowadays in advanced CMOS technologies. Nevertheless, higher readout speeds, single-photon counting capabilities, higher fill-factors, and higher sensitivities are all issues not easy to be solved using standard planar technologies. Moreover, extending the spectra of the radiation to be detected beyond the visible spectra becomes only possible if different materials are used that are not necessarily compatible with the CMOS technology. Currently, hybrid and 3D photodetector technologies are being developed to address these challenges “using the best from several worlds”. But many technical hurdles still need to be addressed. All these developments opened the possibility of using silicon based photodetectors in different scientific applications ranging from spectroscopy, positron emission tomography, neutron detection, or photon science to particle physics. The technological challenges and future perspectives of different silicon based photodetection technologies will be introduced based on several examples.References:1. Amelio G. F. et al. “Experimental verification of the charge coupled device concept”, Bell Syst. Tech. Journal, 49 (4), 593 – 600 (1970)2. Fossum E. R. “CMOS image sensors: electronic camera-on-a-chip”, IEEE IEDM Tech. Digest, 17 – 25 (1995)3. Cova S. et al. “Towards picosecond resolution with single-photon avalanche diodes”, Rev. Sci. Instr., 52, 408 (1981)4. Gasanov A. et al. “Avalanche Detector”, Russian patent No. 1702831 (1989)5. Durini D. and Arutinov D., „Chapter 2: Operational principles of silicon image sensors” in High Performance Silicon Imaging, Ed. Durini D., Woodhead Publishing Ltd. an imprint of Elsevier, UK, p. 25 - 77 (2014