GROUP III METAL NITRIDE FILM AS PHASE TRANSITION MEDIUM FOR OPTICAL RECORDING

摘要

PROBLEM TO BE SOLVED: To provide a phase transition medium for optical recording by preparing a metal compsn. selected from group III metals for a metal nitride thin film. SOLUTION: This phase transition type medium for optical recording is based on a semiconductor comprising group III metal nitrides such as AlN, InN and GaN. By irradiating the surface of this thin film of a semiconductor having a wide band gap with photons of energy equal to or higher than the band gap of the material with higher output density than the threshold, nitrogen is desorbed to form a metal coating. Once nitrogen is desorbed, the metal phase written on the medium can not return to a nitride phase, and this stabilizes the medium as a write-once system. The band gap when a group III metal nitride alloy is used is continuously varied and controlled by changing the relative ratio of III group metals so that the alloy melts by laser having the photon energy laser in the above range. Thus, the material can be used for the format of plural recording layers with low absorbance and high transmittance when proper recording wavelength is used for the initial phase.