[PDF]  https://doi.org/10.3952/physics.v61i2.4438

Open access article / Atviros prieigos straipsnis
Lith. J. Phys. 61, 91–96 (2021)
 

ELECTRON MOBILITY DEPENDENCE ON NEUTRON IRRADIATION FLUENCE IN HEAVILY IRRADIATED SILICON
Juozas Vidmantis Vaitkus, Algirdas Mekys, and Šarūnas Vaitekonis
  Institute of Photonics and Nanotechnology, Vilnius University, Saulėtekio 3, 10257 Vilnius, Lithuania
Email: juozas.vaitkus@ff.vu.lt

Received 12 May 2021; accepted 13 May 2021

An increase of neutron irradiation fluence caused a decrease of Si radiation detector efficiency that was exceptionally well seen at 1017 neutron/cm2 fluence when the observed I–V characteristic of p-n junction under forward bias and under reverse bias became similar. Therefore the investigation of free carrier mobility could be a key experiment to understand the change of heavily irradiated silicon.
The electron mobility was investigated by magnetoresistance means in microstrip silicon samples at temperature range T = 200–276 K. The analysis included the free carrier scattering by phonons, ionized impurities, dipoles and clusters and a contribution of each process was found by fitting the mobility dependence on temperature.
The analysis of experimental data clearly demonstrated that the applied model did not explain the mobility in the samples irradiated to the highest fluence. Therefore a new concept of carrier transport is needed, and, as a conclusion, it could be stated that Si irradiated above 1016 cm–2 fluence (and up to 1020 cm–2) is a disordered material with the clusters.
Keywords: irradiation detector, silicon, mobility
PACS: 61.80.Lj, 72.20.Fr, 77.55.df

STIPRIAI APŠVITINTO NEUTRONAIS SILICIO ELEKTRONŲ JUDRIO PRIKLAUSOMYBĖ NUO NEUTRONŲ ĮTĖKIO
Juozas Vidmantis Vaitkus, Algirdas Mekys, Šarūnas Vaitekonis

Vilniaus universiteto Fotonikos ir nanotechnologijų institutas, Vilnius, Lietuva
Didinant greitųjų neutronų įtėkį, krinta Si radiacinių detektorių naudingumas. Tai aiškiausiai matosi įtėkį padidinus iki 1017 n/cm2, kai p-n jungties voltamperinė charakteristika tiesiogine ir priešinga kryptimis susivienodina. Tokios medžiagos laisvųjų krūvininkų judrio tyrimai galėtų atskleisti apšvitinto Si savybių pasikeitimus.
Darbe krūvininkų judris buvo nustatomas iš magnetovaržos reiškinio mikrostripelių pavidalo Si bandiniuose T = 200–276 K temperatūros intervale. Pernašos reiškiniams analizuoti buvo įskaitoma laisvųjų krūvininkų sklaida fononais, jonizuotomis priemaišomis, dipoliais ir defektų klasteriais. Kiekvieno iš jų indėlis buvo nustatomas atskirai pritaikant judrio temperatūriniam kitimui matematines išraiškas.
Eksperimentinių duomenų analizė aiškiai parodė, kad didžiausio paminėto įtėkio bandiniuose naudojamas pernašos modelis netinka judrio temperatūriniam dėsningumui paaiškinti. Reikalingas naujas modelis šiems pernašos reiškiniams aiškinti, o iš gautų rezultatų galima daryti išvadą, kad Si švitintas įtėkiu per 1016 cm–2 (ir iki 1020 cm–2) yra netvarki medžiaga su defektiniais klasteriais.


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