N. Arutyunov, N. Abrosimov, R. Krause-Rehberg, M. Elsayed, G. Astakhov, S. Akhmadaliev
HZDR, IPLT,
Uzbekistan
Keywords: point radiation defects, radiation tolerance, group–V– impurity complexes, silicon, isotopically-enriched 28–silicon, positron states, deep centers, isochronal annealing
Summary:
Silicon-based devices operating on satellites of quantum communications network accumulate damages generated by the radiation environment of space [1]. For low Earth orbit satellites the irradiation with ≈ 8–15 MeV protons is main source of the point radiation defects production causing irreversible decrease of high-fidelity global quantum communications network [2]. We applied the positron annihilation lifetime spectroscopy (PALS) in order to gain deeper insight into microstructure of the donor atoms of phosphorus, P (J = 1/2), and bismuth, Bi(J = 9/2), to be used as both the qubit-forming elements and dopants in silicon single-photon detectors. The attention is drawn to salient both the reliable and problematic data obtained for moderately doped n–type silicon grown by floating zone (FZ) technique [3,4,5,6]. For the first time, we demonstrate the influence of non-local interaction of the spin systems on the essentially local phenomenon of emission of two-quantum electron-positron annihilation radiation out of the volume ambient the group–V impurity atom in silicon. Both the profoundly isotopcally-enriched 28–Si (a so-called “semiconductor vacuum”) and 28–Si:Bi materials were studied as well. Positron-containing exciton-like states, a polyelectronic exciton are suggested [3, 5]. The radiation tolerance of qubit-forming centers of Bi(J = 9/2) and P(J = 1/2) is discussed in the light of some challenging issues in identification of group–V– impurity complexes with open volume (Vop) in silicon, [Vop – Bi] and [Vop – P]. These defects were found to be dominated in the investigated materials after irradiation with the both 15 MeV protons and ≈1 MeV electrons. The complex [Vop – Bi] having, as it is argued on the basis of experimental and calculated ab initio data [3, 8], D3d symmetry, is decomposed during isochronal annealing over the high-temperature range ΔTann.= 320 to 470 °C; this range is ≈300 to ≈650 °C for the Si: P material [4,7]. These thermally stable complexes of radiation origin in n–type FZ silicon have been elusive from observation for more than five decades. For low Earth orbit satellites where the most damaging factor is the proton irradiation the formation of thermally stable [Vop – Bi] and [Vop – P] complexes will dominate [3-7] in the Si:Bi and Si:P materials. This dominance is surprising and inviting us to reconsider a whole conception of formation of point radiation defects that is generally accepted in the literature for n–type FZ silicon. [1] B. A. Wilson et al., Phys. Rev. Appl., 16 (2021) 064049. [2] J. V. Logan et al., J. Appl. Phys., 134 (2023) 225701. [3] N. Arutyunov et al., J. Phys.: Condens. Matter, 33 (2021) 245702. [4] N. Arutyunov et al., J. Phys.: Condens. Matter, 25 (2013) 035801. [5] N. Arutyunov et al., Trans. Tech. Pub. 2024, in press. [6] N. Arutyunov et al., Phys. Stat. Sol. (c) 13 (2016) 807; ibid. 14 (2017) 1700120. [7] N. Arutyunov et al., Journal of Physics: Conf. Ser. 618 (2015) 012013. [8] H. Höhler et al., Phys. Rev. B, 71 (2005) 035212.