Magnetic-field-induced unbinding of the off-well-center singlet state in multiple quantum wells

Results of far-infrared Fourier-transform magnetotransmission from two (Formula presented) multiple quantum well samples δ-doped with Si-donor on- and off-well centers are compared. In contrast to well-center (Formula presented) ions, the off-well-center (Formula presented) singlet binding energy decreases with increasing magnetic field between 5.5 and 15 T, as reflected by the decreasing strength of the (Formula presented) singlet transition and a consequent increase of the neutral donor (Formula presented) transition. This observation represents a verification of the predicted magnetic-field-induced unbinding (magnetic evaporation) of shallow impurity states for the off-well-center (Formula presented)-ion system.