Surface oxidation and oxygen incorporation in ScAlN films grown by molecular beam epitaxy

Recently, there has been much interest in the ScAlN alloy, thanks to its various potential applications in high-frequency high-power, acoustoelectric, and ferroelectric devices. Nonetheless, these applications could be impaired by the presence of oxygen in the alloy and the formation of a surface oxide layer due to the high affinity of scandium with such impurity. A current trend is to increase the Sc content and most of the time it is accompanied by a lowering of the growth temperature. As it probably strongly influences the incorporation of impurities, we have carefully studied the effects of growth temperature and Sc content in the surface oxide and oxygen content of ScAlN films grown by ammonia source molecular beam epitaxy. The oxygen concentration and bonding configuration have been determined by combining normal-incidence, angle resolved, and ion-etching x-ray photoelectron spectroscopy.