Fe onto GaN(0 0 0 1) grown in a full MOVPE process

To date successful spin injection in spintronics devices has been reported for two different experimental approaches: using diluted magnetic semiconductors or ferromagnetic metals as spin aligners on top of a semiconductor structure. In this work we present our studies on the deposition of Fe on (0 0 0 1)GaN fully accomplished via metalorganic vapour phase epitaxy (MOVPE). Special attention has been devoted to the Fe nucleation onto the GaN surface and the growth has been monitored online by spectroscopic ellipsometry. The structural and magnetic characterization of the layers has been carried out using high-resolution X-ray diffraction, atomic force microscopy, high-resolution transmission electron microscopy and SQUID magnetometry. Depending on the growth parameters, two different kinds of samples can be fabricated: paramagnetic ones, with Fe-alloy nanocrystals a few nanometers below the sample surface, and ferromagnetic ones, with Fe-rich pits and regions close to the surface. Increasing surface roughening due to the Fe deposition in both types of samples, as well as surface reconstruction could be observed from HRTEM measurements. The presence of Fe in proximity of the surface solely indicates the modest diffusion of the magnetic ions achieved by optimizing the growth parameters.