instruments Article Fabrication of a Hydrogenated Amorphous Silicon Detector in 3-D Geometry and Preliminary Test on Planar Prototypes Mauro Menichelli 1, *, Marco Bizzarri 1,2 , Maurizio Boscardin 3,4 , Mirco Caprai 1 , Anna Paola Caricato 5 , Giuseppe Antonio Pablo Cirrone 6 , Michele Crivellari 4 , Ilaria Cupparo 7 , Giacomo Cuttone 6 , Silvain Dunand 8 , Livio Fanò 1,2 , Omar Hammad Alì 4 , Maria Ionica 1 , Keida Kanxheri 1 , Matthew Large 9 , Giuseppe Maruccio 5 , Anna Grazia Monteduro 5 , Francesco Moscatelli 1,10 , Arianna Morozzi 1 , Andrea Papi 1 , Daniele Passeri 1,11 , Marco Petasecca 9 , Silvia Rizzato 5 , Alessandro Rossi 1,2 , Andrea Scorzoni 1,11 , Leonello Servoli 1 , Cinzia Talamonti 7 , Giovanni Verzellesi 3,12 and Nicolas Wyrsch 8   Citation: Menichelli, M.; Bizzarri, M.; Boscardin, M.; Caprai, M.; Caricato, A.P.; Cirrone,G.A.P.; Crivellari, M.; Cupparo, I.; Cuttone, G.; Dunand, S.; et al. Fabrication of a Hydrogenated Amorphous Silicon Detector in 3-D Geometry and Preliminary Test on Planar Prototypes. Instruments 2021, 5, 32. https://doi.org/10.3390/ instruments5040032 Academic Editor: Antonio Ereditato Received: 23 July 2021 Accepted: 28 September 2021 Published: 8 October 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 INFN, Sez. di Perugia, via Pascoli s.n.c., 06123 Perugia, Italy; marco.bizzarri@unipg.it (M.B.); mirco.caprai@pg.infn.it (M.C.); livio.fano@pg.infn.it (L.F.); maria.ionica@pg.infn.it (M.I.); keida.kanxheri@pg.infn.it (K.K.); francesco.moscatelli@pg.infn.it (F.M.); arianna.morozzi@pg.infn.it (A.M.); andrea.papi@pg.infn.it (A.P.); daniele.passeri@unipg.it (D.P.); alessandro.rossi@pg.infn.it (A.R.); andrea.scorzoni@unipg.it (A.S.); leonello.servoli@pg.infn.it (L.S.) 2 Dipartimento di Fisica e Geologia dell’Università degli Studi di Perugia, via Pascoli s.n.c., 06123 Perugia, Italy 3 INFN, TIPFA Via Sommarive 14, 38123 Povo, TN, Italy; boscardi@fbk.eu (M.B.); giovanni.verzellesi@unimo.it (G.V.) 4 Fondazione Bruno Kessler, Via Sommarive 18, 38123 Povo, TN, Italy; crivella@fbk.eu (M.C.); ohammadali@fbk.eu (O.H.A.) 5 INFN and Department of Mathematics and Physics “Ennio de Giorgi” University of Salento, Via per Arnesano, 73100 Lecce, Italy; Annapaola.Caricato@le.infn.it (A.P.C.); giuseppe.maruccio@unisalento.it (G.M.); annagrazia.monteduro@unisalento.it (A.G.M.); silvia.rizzato@unisalento.it (S.R.) 6 INFN Laboratori Nazionali del Sud, Via S.Sofia 62, 95123 Catania, Italy; pablo.cirrone@infn.it (G.A.P.C.); giacomo.cuttone@lns.infn.it (G.C.) 7 INFN and Dipartimento di Fisica Scienze Biomediche sperimentali e Cliniche “Mario Serio”, Viale Morgagni 50, 50135 Firenze, FI, Italy; ilaria.cupparo@unifi.it (I.C.); cinzia.talamonti@unifi.it (C.T.) 8 Ecole Polytechnique Fédérale de Lausanne (EPFL), Institute of Microengineering (IMT), Rue de la Maladière 71b, 2000 Neuchâtel, Switzerland; sylvain.dunand@epfl.ch (S.D.); nicolas.wyrsch@epfl.ch (N.W.) 9 Centre for Medical Radiation Physics, University of Wollongong, Northfields Ave, Wollongong, NSW 2522, Australia; mjl970@uowmail.edu.au (M.L.); marcop@uow.edu.au (M.P.) 10 CNR-IOM, via Pascoli s.n.c., 06123 Perugia, Italy 11 Dipartimento di Ingegneria dell’Università degli studi di Perugia, via G.Duranti, 06125 Perugia, Italy 12 Dipartimento di Scienze e Metodi dell’Ingegneria, Università di Modena e Reggio Emilia, Via Amendola 2, 42122 Reggio Emilia, Italy * Correspondence: mauro.menichelli@pg.infn.it Abstract: Hydrogenated amorphous silicon (a-Si:H) can be produced by plasma-enhanced chemical vapor deposition (PECVD) of SiH 4 (silane) mixed with hydrogen. The resulting material shows outstanding radiation hardness properties and can be deposited on a wide variety of substrates. Devices employing a-Si:H technologies have been used to detect many different kinds of radiation, namely, minimum ionizing particles (MIPs), X-rays, neutrons, and ions, as well as low-energy protons and alphas. However, the detection of MIPs using planar a-Si:H diodes has proven difficult due to their unsatisfactory S/N ratio arising from a combination of high leakage current, high capacitance, and limited charge collection efficiency (50% at best for a 30 μm planar diode). To overcome these limitations, the 3D-SiAm collaboration proposes employing a 3D detector geometry. The use of vertical electrodes allows for a small collection distance to be maintained while preserving a large detector thickness for charge generation. The depletion voltage in this configuration can be kept below 400 V with a consequent reduction in the leakage current. In this paper, following a detailed description of the fabrication process, the results of the tests performed on the planar p-i-n structures made with ion implantation of the dopants and with carrier selective contacts are illustrated. Instruments 2021, 5, 32. https://doi.org/10.3390/instruments5040032 https://www.mdpi.com/journal/instruments