are expected to be introduced into optical recording technology in the next 5 years the band gap of alloys of nitrides of column iii metals can be tuned by changing the relative fractions of the column iii metals to continuously vary the band gap so as to be compatible with lasers having photon energies within the range the low absorptivity and hence high transmissitivity at the appropriate recording wavelength of the starting phase also offers the potential application of these materials in a multiple recording layer format application_number US 89282697 A description this invention provides phase change media for optical storage based on semiconductors formed of nitrides of the column group iii metals of the periodic table and nitrogen e g ain inn and gan alloys of the column iii metals with nitrogen e g ingaain have been found to be useable and to offer unique properties in that their bandgaps can be tailored or tuned by adjusting the alloy composition to thereby match the wavelength of the beam used for writing fig1 shows the structure of an ain phase change media in schematic cross section to form this structure ain was deposited onto a sapphire substrate by directing evaporated al and reactive nitrogen created by radio frequency rf discharge towards the substrate in high vacuum the choice of substrate can be varied sapphire is used as an example only also the rf deposition technique is an example and other deposition techniques may be used the ain thin film in this case was about 300 nm thick following deposition the sample was removed from the vacuum chamber and the surface of the ain irradiated with 248 nm ultraviolet uv light radiation from an excimer laser the radiation was supplied at an energy density of 100.