Properties of GeSbSn Layer Used as Phase-Change Recording Medium

Abstract

This paper is to study the properties of phase-change material of GeSbSn used in blue-ray disks and high-speed DVDs, especially on different ratio between Sb and Sn, as well as their crystallization rate, through a series of optical, thermal, and dynamic testings. For GeSbSn material system, there are two exothmal peaks under a condition of high Sn content in the material. For our four samples of GSS01-GSS04, the smaller the ratio of Sb/Sn, the lower the temperature of first exothermal peak. It means that the write-in power of high-speed DVD disk can be decrease. However, the thermal stability due to the activation energy of crystallization increases with the Sb/Sn ratio. By optical measurements for these samples, the optical contrast is greater than 0.6 at a wavelength of 650 nm and that than 0.5 at a length of 405 nm. All of them are meet the requirements of 4X speed DVD. In dynamic test, the modulation of readout signal for GSS01-GSS02 decresses below 0.5 as the ratio of Sb/Sn becomes lower, while the jitter at 14T for GSS04 is over 12% as the ratio of Sb/Sn is too high be used. Consequently, only GSS03 (Ge₁₄Sb₆₄Sn₂₂(at%)) can be used in 4-12X speed DVD-RW or 1-3 X speed blue-ray disk.