Abstract: Spatially localized radiation, preferably ultraviolet visible radiation, representing information is impinged onto a spatially localized area of a heterostructure comprising a ternary Group III-V Nitride semiconductor material. It has been found that the spatially localized optical radiation reversibly changes the properties of the heterostructure comprising ternary Group III-V Nitride semiconductor material in the spatially localized area, to thereby provide an optical memory. The stored information can be read from the memory by impinging blanket radiation, preferably ultraviolet radiation of the same frequency which was used to write the information, onto the heterostructure comprising ternary Group III-V Nitride semiconductor material including onto the spatially localized area thereof.