Effect of oxygen on structural stability of nitrogen-doped germanium telluride films with and without silicon nitride layer

Nitrogen-doped germanium telluride (N-GeTe) films with and without silicon nitride (SiN) layer were thermally annealed in an air atmosphere. The SiN layer prevented the oxidation of GeTe films despite the massive in-diffusion of oxygen atoms. The phase transition from cubic to rhombohedral phase occurred only in the air-annealed samples, not in the samples annealed at 2.0 mPa. The in-diffused oxygen is probably the leading cause of this phase transition. N-GeTe films without SiN layer showed an increase in sheet resistance after 1000 min of air annealing; this could be attributable to a phase transition from the cubic GeTe phase to the amorphous germanium oxide and metallic tellurium phases.

► SiN layer prevented oxidation of GeTe despite the massive in-diffusion of oxygen.
► The in-diffused oxygen have a critical role in the changes of crystal structure.
► N-GeTe exhibited phase transition into amorphous Ge oxide and metallic Te phase.