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 Mn 6 N 2.58 and Mn 3 N 2 , 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 Ϫ1 decreased drastically as annealing temperature increased ͑Ͼ800°C͒, 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.

Comparison of GaMnN epilayers prepared by ion implantation and metalorganic chemical vapor deposition

“…Also visible in some scans are peaks from the antiferromagnetic compounds Mn 6 N 2.58 and Mn 3 N 2 . Similar nonstoichiometric phases have been observed previously in MBE grown [8] and heavily-annealed implanted samples [9]. Ion implantation introduces an excess of Gallium site cations; the annealing conditions are not suitable for the replenishment of nitrogen and subsequent rearrangement of a 1:1 stoichiometric crystalPhase separation can occur even at temperatures that have been reported as suitable for GaMnN annealing [9].…”

“…Increased antiferromagnetic Mn-Mn superexchange interactions would result from Mn atom nearest-neighbor clustering. In addition, secondary phases, including the antiferromagneic Mn x N y compounds are known to form at elevated temperatures annealing [9].Annealing in a nitrogen atmosphere also drives out any residual hydrogen from the layers; hydrogen has been shown to aid the magnetic behavior by passivation of defect states [13]. Similarly, annealing can introduce a nitrogen vacancies which act as shallow donors, driving the Fermi level towards the valence band.…”

Multifunctional III-nitride dilute magnetic semiconductor epilayers and nanostructures as a future platform for spintronic devices

“…The band at 3.0 eV is attributed to Mnrelated or Mn-induced transitions for heavily Mn doped samples. Recently, the blue band emission was observed in MBE-grown GaMnN [49], and the appearance of these bands was assigned to transitions from conduction band electrons to Mn -related states and from shallow donor (e.g., N vacancy) to Mn acceptor states [42][43][44]50].…”

Single phase nanocrystalline GaMnN thin films with high Mn content

“…Furthermore, GaN doped with magnetic elements such as Mn, [1][2][3][4][5][6] Cr, [7][8][9] or the rare earths 10,11 has received much attention because of its potential to allow manipulation of the spin degree of freedom of the charge carriers by introducing a net magnetic moment. Experimental studies of nanocrystalline and amorphous [12][13][14] GaN thin films have supported predictions 15 that even in a heavily disordered state many of the useful properties of the single crystalline material are retained.…”