Effect of InP Doping on the Phase Transition of Thin GeSbTe Films

We report the crystallization and phase-transition behavior of GeSbTe thin films doped with indium phosphorus (InP). Pure GeSbTe thin films and InP-doped GeSbTe thin films were prepared by use of an rf magnetron sputtering method. After thermal annealing, electrical and optical changes in the thin films were observed. Sheet resistance and reflectance measurements revealed that InP doping suppresses crystallization of GeSbTe. X-ray diffraction analysis confirmed that addition of In and P atoms inhibits the phase transition from face-centered cubic to hexagonal closed-packed. Nucleation of the doped GeSbTe thin films was delayed at an annealing temperature of 100A degrees C; after thermal annealing, neither segregation nor formation of a secondary phase occurred. These results indicate that InP doping improves the amorphous stability of GeSbTe thin films. It is believed this enhanced amorphous stability is a result of the formation of multiple, strong crosslinks by the In and P atoms.