Excimer laser annealing: An alternative route and its optimisation to effectively activate Si dopants in AlN films grown by plasma assisted molecular beam epitaxy

Abstract

Si doped AlN films were grown on GaN/Sapphire templates by plasma assisted molecular beam epitaxy (PAMBE) technique. We show that employing an excimer laser annealing with optimized power and frequency rather than the conventional thermal annealing could be a potential alternative route towards improving the structural and electrical properties of AlN layers. Upon optimized laser annealing of the Si-doped AlN layer, the electron concentration was achieved to be as high as ∼4.9×1018cm−3 which was measured by Raman spectroscopy measurement and was further cross checked by standard Hall measurement which estimated the same as ∼7.4×1018cm−3 with a mobility of 109cm2/V-sec. The improvement of free carrier concentration was leveraged by improvement of structural properties. The r.m.s surface roughness of the Si-doped AlN layers measured by atomic force microscopy was reduced to 0.76nm and corresponding residual stress estimated by high resolution XRD and Raman measurement was found to be less than half compared to the in-situ Si-doped sample. Thus laser annealing is proposed to be a suitable method to achieve high electron concentration in Si doped AlN films without compromising the structural quality.