Solid electrolyte containing oxynitride, and secondary battery including the solid electrolyte

A secondary battery comprising:

• a solid electrolyte including an oxynitride that contains an alkaline-earth metal, phosphorus, oxygen, and nitrogen;
• a positive electrode;
• and
• a negative electrode,
• wherein a P2p spectrum obtained by an X-ray photoelectron spectroscopy measurement of the oxynitride contains a peak component originating from a P—N bond.

A method for producing an oxynitride of alkaline-earth metal, comprising performing a process cycle including:

• (A) supplying a first precursor containing phosphorus over a substrate;
• (B) supplying at least one of an oxygen gas and an ozone gas over the substrate;
• (C) supplying a second precursor containing alkaline-earth metal over the substrate;
• (D) supplying at least one of a nitrogen gas and an ammonia gas over the substrate;
• and
• (E) supplying a purge gas over the substrate,
• wherein the process cycle is performed one or more time,
• in one process cycle, (A) and (C) are performed in different periods, and (E) is performed one or more times.