A method of forming a silicon nitride layer or film on a semiconductor wafer structure includes forming a silicon nitride layer on the surface of a wafer structure using a molecular beam of high purity elemental Si and an atomic beam of high purity nitrogen. In a preferred embodiment, a III-V compound semiconductor wafer structure is heated in an ultra high vacuum system to a temperature below the decomposition temperature of said compound semiconductor wafer structure and a silicon nitride layer is formed using a molecular beam of Si provided by either thermal evaporation or electron beam evaporation, and an atomic nitrogen beam provided by either RF or microwave plasma discharge.