Abstract: A predetermined initialization is made on a CD-R disc or a CD-RW disc using an existing formatting method to a specific disc on which recorded are a media number forming an encryption key based on a combination of a decimal six-digit disc ID, a decimal thirteen-digit MCN and a decimal five-digit ISRC serial number and encrypted data obtained by the encryption using this media number. This allows a user to make the copy of copyrighted data such as music, movie and computer program data only once, but inhibits the secondary copy from this copy disc to another disc, which achieves the protection of the copyrighted data.

Abstract: An epitaxial wafer for producing arrays of GaAsP-LEDs comprises, in the GaAs.sub.1-x P.sub.x layer with varying X, a layer region(s) with a discontinuous variance of x along the thickness of the GaAs.sub.1-x P.sub.x layer. This layer region(s) contribute to a uniformity in the brightness of the light emission of LEDs formed in the epitaxial wafer.

Abstract: An epitaxial wafer for producing arrays of GaAsP-LEDs comprises, in the GaAs.sub.1-x P.sub.x layer with varying X, a layer region(s) with a discontinuous variance of x along the thickness of the GaAs.sub.1-x P.sub.x layer. This layer region(s) contribute to a uniformity in the brightness of the light emission of LEDs formed in the epitaxial wafer.

Abstract: In a GaAs epitaxial wafer including, for example, two epitaxial layers having high and low carrier concentrations, the carrier concentration of the low carrier concentration layer is liable to greatly vary, so that wafers suitable for FETs and Schottky barrier diodes operated at UHF and SHF are produced at only a low yield. This drawback is eliminated by adjusting the heating temperature of GaAs substrate to 690.degree. to 730.degree. C. during the growth of the low carrier concentration layer.