Microstructural, optical, and magnetic properties of Mn-implanted p-type GaN

Abstract

The effect of microstructural change on both magnetic and optical properties of Mn-implanted p-type GaN was studied. A dilute magnetic semiconductor was achieved by implanting Mn ions into p-type GaN and subsequently annealing. The magnetization measurement showed that the Curie temperature was the highest in the 800 °C annealed sample due to the formation of Ga–Mn magnetic phases. The annealing at a higher temperature of 900 °C produced antiferromagnetic Mn–N compounds such as Mn6N2.58 and Mn3N2, leaving N vacancies. This provides evidence that N vacancies played a critical role in weakening the ferromagnetic property in the Mn-implanted GaN. The photoluminescence peak at 2.92 eV became strong after annealing at 800 °C, indicating an increase in hole concentration due to an enhanced activation of Mn impurities in p-type GaN. The intensity of Raman modes at 290 and 670 cm−1 decreased drastically as annealing temperature increased (>800 °C), due to the reduction in Mn-implantation-induced lattice imperfections. From this, it is proposed that the increase in magnetic properties of Mn-implanted GaN originated from the enhancement in the crystallinity as well as the production of Ga–Mn magnetic phases.