Comparative study of Mn and Fe incorporation into GaN by metalorganic chemical vapor deposition

Abstract

Wide bandgap diluted magnetic semiconductors (DMS) have been of interest recently due to theoretical predictions of room temperature ferromagnetism in these materials. However, the mechanism of the observed ferromagnetism of the nitrde-based DMS is still controversial, and may originate from a carriermediated, defect-related or nanoscale clustering mechanism. In this work, we present a comparative study of the incorporation of various transition metals and their effect on the optical, structural, and magnetic properties of GaN. Metal-organic chemical vapor deposition (MOCVD) has been employed to produce epitaxial films of varying thickness and manganese and iron concentrations using bis-cyclopentyldienyl (magnanese, iron) as the transition metal sources. High-resolution X-ray diffraction reveals no macroscopic secondary phases under optimized growth conditions. Magnetic hysteresis is observed at room temperature in both Ga 1-x Mn x N and Ga 1-x Fe x N, though the strength of the magnetic ordering is roughly an order of magnitude weaker in the Fe-alloyed samples. Increasing Mn concentrations significantly affects the long-range lattice ordering, and the observation of local vibrational modes (LVMs) supports the formation of nitrogen vacancies, even under optimized MOCVD growth conditions. Such vacancies form shallow donor complexes and thus contribute to self-compensation. Disorder-induced modes at 300 cm -1 and 710 cm -1 and a LVM due to vacancies at 669 cm -1 were revealed by Raman spectroscopy. The irondoped samples also show the disorder-induced modes, but the vacancy-related mode is not observed which is attributed to Fermi level and defect formation energy considerations.

Pressure effect on impurity local vibrational mode and phase transitions in n-type iron-doped indium phosphide

“…4(a) shows the enlarged plot for Fe LVM. The appearance of LVM is likely due to a relaxation of the Raman selection rules associated with the iron-induced defects in the system 34 . Sun et al .…”

ParamagneticGaN:Feand ferromagnetic(Ga,Fe)N: The relationship between structural, electronic, and magnetic properties

“…17 The metalorganic chemical vapor deposition (MOCVD) of GaN:Fe has been previously reported, with a focus on the actual Fe content in the layers and its effect onto the carrier concentration. 18 More recent preliminary works by others 19 and us 20,21 indicate that MOCVD grown (Ga,Fe)N shows ferromagnetic-like characteristics to above room temperature. Moreover, diluted magnetic semiconductors, and (Ga,Fe)N in particular, have become model systems to test various implementations of the density functional theory to disordered strongly correlated systems.…”

GaN:Co epitaxial layers grown by MOVPE

“…On the other hand, many groups have already reported ferromagnetism in various transition and rare earth metal doped AIII nitride layers [6][7][8][9][10][11]. Ferromagnetic ordering above room temperature was obs erved for GaN layers doped with Mn [12,13], Cr [14,15], Fe [16] and lanthanide atoms, like Gd [17,18] and Dy [19][20][21]. Both MOVPE and MBE techniques were used for the growth of these layers.…”