Optical excitation of spin-triplet states of two-electron donors in silicon
Tsyplenkov V.V.1, Zhukavin R.Kh.1, Shastin V.N.1
1Federal Research Center A.V. Gaponov-Grekhov Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, Russia
Email: Tsyplenkov1@yandex.ru

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In this paper, we propose a method for resonant optical excitation of ortho states of two-electron donors in silicon, direct transitions to which from the ground state are extremely suppressed in case of a weak spin-orbit coupling. Excitation is proposed to be carried out using the points of anti-crossing of ortho and para states under conditions of uniaxial stress of the crystal. In these points the states cannot be unambiguously assigned to any group of states with a certain spin, as a result of which the optical transition becomes allowed. The structure of the energy levels of two-electron impurities is such that the excitation of such state almost unambiguously leads to the population of the underlying ortho-type state, which is expected to be very long-lived in the case of weak spin-orbit coupling. In the present work, theoretical estimates of the cross sections for optical transitions in the vicinity of the level anticrossing point as a function of strain for strong and weak spin-orbit coupling are made. Keywords: doubly charged donors, para and ortho states, optical transitions, spin-orbit interaction.
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