Probing States of a Double Acceptor in CdHgTe Heterostructures via Optical Gating

Photoconductivity spectra in a HgTe/CdHgTe double quantum well with a normal band structure have been studied. Photosensitivity bands associated with the ionization of a mercury vacancy, which is a doubly charged acceptor, have been detected in photoconductivity spectra. The transformation of photoconductivity spectra when the Fermi level moves from the edge of the valence band through the band gap to the conduction band has been revealed using the residual photoconductivity effect. It has been shown that the observed absorption bands are due to the ionization of doubly charged acceptors rather than individual different singly charged states.