Optical Transition of Chalcogenide Phase-Change Thin Films

概要

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The optical transitions of as-deposited and thermally annealed chalcogenide phase-change thin films were studied. Allowed indirect transition occurs in Ge, GeTe, and Ge2Sb2.3Te5 and allowed direct transition in Sb, Sb2Te3, Ge1Sb1Te2, Ge1Sb2Te4, Ge1Sb4Te7, and Ge2Sb2Te5. For both amorphous and crystalline states, optical energy gap $E_{\text{g}}^{\text{opt}}$ decreases with increasing film thickness due to the blue shift effect. $E_{\text{g}}^{\text{opt}}$ of crystalline is ${\sim}0.5$ eV lower than their amorphous counterparts. $E_{\text{g}}^{\text{opt}}$ has a linear proportional relationship with the percentage of partial crystalline phases $R_{\text{pc}}$. The different kinds of optical transition and the decrease of $E_{\text{g}}^{\text{opt}}$ between Ge2Sb2Te5 and Ge2Sb2.3Te5 may be attributed to the structural change, caused by the presence of the additional Sb as a structure modifier, which changes the interaction among the components of the Ge2Sb2Te5 system.
INSTITUTE OF PURE AND APPLIED PHYSICSの論文
2003-02-15