M-plane GaN epifilms doped with Mn grown by PAMBE*

Nonpolar m-plane gallium nitride (m-GaN) epifilms were grown on the substrate of m-plane sapphires using the plasma-assisted molecular beam epitaxy (PAMBE) system. One series was to vary the nitrogen plasma power to obtain a uni-phase epitaxial film and another was to vary the growth temperature to obtain a metal-free high-quality sample. The metal droplets started to appear when it was in the lower power range while the droplet size increased and the density reduced with reducing power. X-ray diffractometry revealed a uni-phase structure at lower power and a multi-phase structure at higher power. Further increase of the growth temperature removed the surface metal and improved the quality of the epitaxial film further. Strain analysis was performed through Raman spectroscopy and the result is explained by the lattice mismatch between the epifilm and the substrate. Transition metal manganese (Mn) doping into the m-GaN was explored for room temperature ferromagnetism. Magnetic measurements along with x-ray photoelectron spectroscopy and x-ray absorption spectroscopy were done.