Structure and element composition of the nitride layer of AlN/Al2O3 templates obtained by the thermochemical nitridation of sapphire

Abstract

Aluminum-nitride layers on sapphire (AlN/sapphire templates) are obtained by the thermochemical nitridation (TCN) of sapphire substrates. According to X-ray diffraction data, AlN layers have a singlecomponent texture with the axis [0001] and high structural perfection (the rocking curve half-width β is 15′–30′). The nitride-layer depth reaches 1 μm. The structure and element composition of the nitride layer were studied via the step-by-step removal of the nitride layer while polishing the AlN/sapphire templates. The study of the element composition of the nitride surface by X-ray photoelectron spectroscopy during the process of the step-by-step removal of the nitride layer reveals a gradual decrease in the concentration of nitrogen atoms confirming the diffusion mechanism of sapphire nitridation. Characterization of the surface morphology of the polished AlN/sapphire templates by means of atomic-force microscopy shows the presence of pores in it. The formation of these pores can be caused by the dissociative decomposition of sapphire in reducing-gas media upon TCN followed by the formation of gaseous products which form the pores upon reaching the surface.