Doping of GaN with Mn and Cr has been achieved by metal organic chemical vapor deposition (MOCVD). Hysteretic behavior was observed at room temperature and structural measurements, X-ray diffraction, and atomic force microscopy gave no evidence of second phases in the transition metal-doped epitaxial layers. Multilayer structures grown by MOCVD were used to determine the dependence of magnetic ordering in GaMnN and GaCrN epilayers upon the availability of free holes. Based on these results a prototype spin devices were designed and fabricated in which holes, adjacent to a GaMnN or GaCrN layer, could be modulated by an applied electric field. The devices demonstrated that enhancement of ferromagnetic behavior could be switched on and off electrically at room temperature. Such current-controlled FM in GaMnN or GaCrN devices would have important applications at room temperature, especially in nonvolatile memory storage systems.