Changes in the Hall coefficient and Fermi level (EF) at T = 300 K as a function of the flux (Tirr ≦ 50°C) of 60Co and stopping spectrum (Emax = 100 MeV) γ‐rays, electrons (2.5 to 10 MeV), protons (640 MeV), and fast reactor neutrons in float‐zone and pulled n‐ and p‐type Si are studied. It is found that for all kinds of irradiation, the floated zone n‐type Si changes the type of its conductivity and a Fermi level stabilization takes place within some range of particle fluxes at Ev + 0.48 eV (proton and neutron irradiation) or at Ev + 0.39 eV (60Co γ‐rays, electrons). The Fermi level stabilization at Ev + 0.48 eV is concluded to be determined by the accumulation at dominant concentrations of divacancies having donor, (Ev + 0.28 eV), and acceptor, (Ec −0.40 eV), levels in the forbidden gap and the Fermi level stabilization at Ev + 0.39 eV the accumulation of multicharge complexes involving primary radiation defects and residual impurities (possibly, carbon). The Fermi level position near the middle of the forbidden gap at Ev + (0.54 ± 0.03) eV, which is achieved during prolonged irradiation, is due to the accumulation of vacancy and interstitial types of intrinsic structural damages, being annealed at T = 80 to 150°C.
Comparative experiments are made to study the nonequilibrium charge‐carrier recombination in silicon irradiated with γ‐rays of 50Co and of the bremsstrahlung spectrum of electrons with maximum energy 100 MeV. n‐ and p‐Si crystals with ϱ = 10 to 1000 Ωcm grown by Czochralski and vacuum float‐zone techniques are used. The temperature and injection dependences of nonequilibrium charge‐carrier lifetimes measured by a phase method are analyzed. It is found that when irradiating with γ‐rays of 60Co a great number of recombination centers are produced which are mainly complexes of irradiation‐generated vacancies and interstitials with dopants (phosphorus, boron) and technological (oxygen, carbon) impurities. As distinct from this, the dominant recombination centres in silicon irradiated with γ‐rays of the bremsstrahlung spectrum are divacancies involved in defect clusters, surrounded by the potential barrier Ψ for the majority charge carriers. The parameters of recombination centres (energy level spectrum, annealing temperatures, charge‐carrier capture coefficients) in crystals studied under γ‐irradiation are determined. The peculiarities in the charge‐carrier recombination processes due to the localization of recombination centres in defect clusters generated by photonuclear reaction products are discussed.
The production of radiation defects in float-zone and pulled n-Si (e = 1 to 500 Qcm) irradiated by protons with energy 16,30,660, and 8600 MeV a t T 5 320 K is studied. The changes in the initial rates of charge-carrier concentration and Hall mobility decrease under irradiation as a function of residual (technological) and doping impurity content are analysed. It is concluded that the impurity content has weak influence on radiation defect production processes under this irradiation.IEaK paaiwepbi ~n e p -~~e p r~e t 2 npoToHoB. Jle@eKTOB, 9 T O IlOCJIy?fMJIO OCHOBaWEi eM AJIR OUeHKH pa3MepOB Rnpa M npMMeCH0-3HaYHTeJIbHOg Mepe KOHUeHTpaUHe~ IIPHCYTCTBYIoWIlX B KpMCTaJIJIe IIpHMeCefi, TOrAa
Rearrangement processes proceeding during annealing of electrically active radiation defects in heavily irradiated (30 MeV protons) Si when the concentration of primary defects induced exceeds the concentration of impurities available in crystal are studied. Czochralski grown and vacuum floating-zone n-and p-type silicon (e = 3 to 500 R um) are used. Experimental results obtained from the analysis of the Hall coefficient temperature dependences show that the rearrangement of intrinsic structural defects (diinterstitials and multivacancy complexes) occurs predominantly during annealing. Accumulation kinetics is studied and temperature stability range of some multivacancy complexes contributing to the forbidden gap energy levels E, + 0.29 eV (400 to 650 "C), E, + 0.32 eV (500 to 750 "C), E, + 0.22 eV (500 to 700 "C), E, + 0.15 eV (500 to 800 "C), E , + + 0.10 el' (600 to 750 "C), E, -0.24 eV (500 to 850 "C) most of which are acceptor levels is dctermined. The diinterstitial (Si-B3) center being annealed in the tempernturc range 300 to 500 "C is supposed to be a multicharge defect and has deep acceptor (> E, -0.40 eV) and donor
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