Lithuanian Journal of Physics article / Lietuvos fizikos žurnalo straipsnis

CONTROL OF PROTON IRRADIATION-INDUCED DAMAGE IN LOW GAIN AVALANCHE DETECTORS BY HEAT TREATMENT TECHNIQUES
Laimonas Deveikis, Margarita Biveinytė, Tomas Čeponis, Eugenijus Gaubas, Vytautas Rumbauskas, and Kęstutis Žilinskas
Institute of Photonics and Nanotechnology, Vilnius University, Saulėtekio 3, 10257 Vilnius, Lithuania
Email: laimonas.deveikis@tmi.vu.lt

Received 21 October 2025; accepted 16 November 2025

Silicon-based particle sensors are widely employed in high-energy and nuclear physics experiments conducted at the European Organization for Nuclear Research (CERN). In recent years, silicon sensors with internal gain, known as low gain avalanche detectors (LGADs), have demonstrated an excellent performance in detecting high-energy particles owing to their good spatial and timing resolution. The sensor LGAD architecture has shown a great potential for the use in the upcoming High-Luminosity Large Hadron Collider (HL-LHC) upgrade, where semiconductor sensors will be exposed to extremely high radiation fluences. In this study, the impact of high-energy proton irradiation on the electrical performance of LGADs was investigated. The variations of critical parameters such as leakage current, effective doping concentration, carrier lifetime, spectral characteristics of radiation-induced defects, and charge collection, before and after thermal annealing at different temperatures, have been analysed using the I–V, C–V, microwave-probed photoconductivity (MW-PC), photoionization spectroscopy (PIS), and transient current (TCT) methods. It was demonstrated that the 24 GeV energy proton irradiation introduces defects, such as divacancy and trivacancy complexes, boron–oxygen and carbon–oxygen complexes, as well as divacancy–oxygen and divalent bistable defects, which act as current generation and carrier recombination centres. Annealing at temperatures of up to 400°C led to the transformation or passivation of those defects, partially restoring doping profiles and improving carrier lifetimes. These results highlight the potential of defect engineering to enhance the radiation tolerance of LGADs employed in high-energy physics applications.
Keywords: low-gain avalanche detectors, radiation-induced defects, recombination lifetime, spectroscopy of defects

PROTONAIS INDUKUOTOS RADIACINĖS PAŽAIDOS SENSORIUOSE SU VIDINIU STIPRINIMU VALDYMAS TAIKANT TERMINIO APDOROJIMO METODUS
Laimonas Deveikis, Margarita Biveinytė, Tomas Čeponis, Eugenijus Gaubas, Vytautas Rumbauskas, Kęstutis Žilinskas

Vilniaus universiteto Fizikos fakulteto Fotonikos ir nanotechnologijų institutas, Vilnius, Lietuva

Silicio pagrindu sukurti dalelių jutikliai plačiai naudojami aukštųjų energijų ir branduolinės fizikos eksperimentuose, vykdomuose CERN. Silicio jutikliai su vidiniu stiprinimu (vadinamieji Low Gain Avalanche Detectors, LGADs) pasižymi minėtuose eksperimentuose būtina erdvine ir laikine skyra ir laikomi vienu perspektyviausių technologinių sprendimų planuojamam didelio šviesingumo Didžiojo hadronų priešinių pluoštų greitintuvo (High-Luminosity Large Hadron Collider, HL-LHC) atnaujinimui, po kurio jutikliai turės atlaikyti ypač dideles spinduliuotės dozes.
Šiame darbe ištirta didelės energijos (24 GeV) reliatyvistinių protonų spinduliuotės įtaka silicio jutiklių su vidiniu stiprinimu elektrinėms charakteristikoms. Pasitelkus voltamperinių ir voltfaradinių charakteristikų matavimus, mikrobangomis zonduojamo fotolaidumo kinetikų analizę, fotojonizacijos spektroskopiją bei indukuoto krūvio dreifo srovių kinetikų matavimus, buvo ištirti nuotėkio srovės, efektinės legirantų koncentracijos, krūvininkų gyvavimo trukmės, radiacinių defektų spektrinių charakteristikų ir krūvio surinkimo efektyvumo pokyčiai jutikliuose su vidiniu stiprinimu prieš ir po terminių iškaitinimų įvairiose temperatūrose.
Buvo atskleista, kad protonų spinduliuotė sukelia defektų formavimąsi, tokių kaip divakansijų ir trivakansijų kompleksai, boro–deguonies, anglies–deguonies, divakansijos–deguonies kompleksai bei bistabilūs centrai. Šie defektai veikia kaip generaciniai arba rekombinaciniai centrai, nulemiantys jutiklių funkcinių charakteristikų kaitą. Parodyta, kad bandinių iškaitinimas iki 400 °C nulemia radiacinių defektų transformacijas ar dalies jų pasyvaciją, taip pat iš dalies atkuria legirantų koncentracijų pasiskirstymo profilius ir krūvininkų rekombinacijos trukmę. Aptarti rezultatai patvirtina defektų inžinerijos svarbą, siekiant padidinti jutiklių su vidiniu stiprinimu radiacinį atsparumą ir siekiant taikyti juos ateities aukštųjų energijų fizikos eksperimentuose.

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