Effects of Si doping on the ferromagnetic properties of delta doped GaMnN nanorods

Delta doping (δ-doping) of group-III nitride-based nanostructures such as nanorods (NRs) with transition metals such as manganese (Mn) can lead to one-dimensional (1D) diluted magnetic semiconductors (DMSs). In order to investigate the effects of free carrier doping on the structural, electrical, and magnetic properties of such delta-doped 1D structures, we have used nanosphere lithography to grow uniform arrays of vertically aligned NRs with fixed aspect ratios on single crystal Al2O3 substrates using plasma-assisted molecular beam epitaxy (PAMBE). The precise control of the elemental flux intensity and duration, facilitated by PAMBE, enables the growth of phase-pure nanostructures, resulting in spatial separation on the order of few nanometers, between the δ-Mn layer and the free carriers in the Si:GaN layer. Chemical quantification verifies the presence of Mn and Si, while Raman spectroscopy shows that Si doping enhances the local vibration mode associated with Mn bonded to N as well as the disorder-activated mode. The free carriers do not diminish the inherent magnetic ordering in these 1D structures, while magnetic measurements show a stability in the signal.