Speaker
Description
Thin-film semiconductor sensors represent a class of particle detectors that exploit scalable deposition techniques to extend the range of active materials beyond silicon and to ultimately enable large-area, low-mass sensor fabrication on flexible substrates. The active material may be deposited as a standalone film, or directly onto a CMOS readout ASIC, enabling monolithic-like hybrid integration without conventional bump-bonding. This contribution presents an overview of ongoing activities carried out by UC Santa Cruz, Argonne National Laboratory, the University of Hawaiʻi, and Lawrence Berkeley National Laboratory.
Indium Phosphide (InP) is investigated as a crystalline benchmark material, whose substantially higher electron mobility compared to silicon is also of interest for fast-timing applications. Single-pad sensors and pad arrays fabricated on semi-insulating InP:Fe wafers at ANL have been characterised with red-laser TCT, and focused X-ray beams at the Canadian Light Source (CLS) and Diamond Light Source (DLS), with beam test data analysis ongoing. A signal formation model based on electron drift and trapping is fit to the data from neutron-irradiated InP sensors characterized with a Sr-90 beta source at multiple temperatures. 2D and 3D TCAD simulations are underway to further inform the device physics and guide the transition toward InP thin-film deposition.
Amorphous selenium (a-Se) is investigated as a direct-conversion thin-film material compatible with room-temperature deposition onto CMOS substrates. Deposition of a-Se directly onto an ITkPix HEP CMOS readout chip has been demonstrated, with pixel-level performance confirming detection of X-rays and low-energy beta particles. Alloying of a-Se with germanium (Ge) and tellurium (Te) is explored to improve electron transport, and tuning of the band gap and hence spectral response. Multilayer stacking of a-Se and Se-Te layers is pursued as a route to broadband spectral coverage beyond what single-alloy films can achieve.
Amorphous silicon (a-Si) on CMOS is pursued as a further option, extending (or returning) the material comparison to a well-characterised amorphous semiconductor.