Mn and other magnetic impurities in GaN and other III–V semiconductors – perspective for spintronic applications

III–V semiconductors doped with magnetic ions have been attracting interest of many laboratories all over the world during more than thirty years. At the beginning the reason was the will to understand influence of omnipresent unintentional, as well as intentionally introduced, impurities of transition metals or rare earths on electrical and optical properties of semiconductors commonly applied in electronic and optoelectronic devices. In the last years the subject of III–V semiconductors highly doped with magnetic ions, the so-called diluted magnetic semiconductors, has revived rapidly again in the context of the newborn branch of electronics, called spintronics. Diluted magnetic semiconductors based on III–V compounds are regarded as prospect candidates for applications in spintronic devices. The results of studies performed on III–V semiconductors, doped or diluted with different magnetic ions, are presented. Special attention is put to GaN because of a strong hope, based on theoretical calculations, for high temperature ferromagnetism. Reasons for difficulties with obtaining high temperature ferromagnetic semiconductors are shown. A possible mechanism of magnetic ordering in III–V semiconductors doped with Mn is presented.