HYDROGEN-LIKE EXCITATIONS OF 3D TRANSITION-ELEMENT IMPURITIES IN SEMICONDUCTORS

Impurities of 3d elements in II-VI and III-V semiconductors are isoval ent and have a partially filled 3d shell. They accordingly give rise t o energy states. Excited states of the 3d shell (intracenter excitatio ns) are manifested in absorption and luminescence spectra. The number of electrons in the 3d shell does not change. Certain 3d impurities in II-VI compounds exhibit excitations of a new type: An electron goes f rom the 3d shell to a hydrogen-like orbit without breaking its bond wi th the impurity, or an electron from the valence band goes into the 3d shell, while the hole is left in a hydrogen-like orbit. A large amoun t of experimental information on hydrogen-like excitations of 3d impur ities in various semiconductors has been accumulated in recent years. The purpose of this review is to put these results on hydrogen-like ex citations of 3d impurities in a systematic form.