New shallow acceptor magnetoabsorption lines in THz range have been discovered under bandgap photoexcitation in strained Ge/GeSi multiple-quantum-well heterostructures. It is shown, both theoretically and experimentally, that the resonant absorption results from the photoionization of A^+-centers and from 1s → 2p_+-type transitions from the ground state of the barrier-situated A^0-centers into excited states in the 1st and 2nd electronic subbands. The shallowest discovered ground acceptor states (E_B≤0.5 meV) are attributed to the "barrier-spaced" acceptors (a hole bound with an acceptor ion in the neighboring Ge quantum well).
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