Interfacial properties of AlN and oxidized AlN on Si

We report on the characteristics of metal-insulator-semiconductor (MIS) capacitors with aluminum nitride (AlN) as the insulator material. AlN has been grown on (1 1 1) Si by means of molecular beam epitaxy (MBE) and DC magnetron sputtering (SPU). AlN layers have been characterized before and after dry thermal oxidation in O₂. By analyzing changes in morphology and electrical properties, different oxidation mechanisms were identified, due to the crystalline quality difference of the AlN samples. In both cases, oxidation at 1000 °C was beneficial for the electrical characteristics of the MIS structures, presumably due to passivation of atom vacancies. Although AlN was only partially oxidized, the flat-band voltage was reduced and the density of interface traps improved. Dominant conduction mechanism was Poole-Frenkel for the SPU sample, and changed to hopping after oxidation.