Indium selenide (In2Se3) thin film for phase-change memory

A cross-point type phase-change random access memory (PRAM) device without an access transistor is successfully fabricated with the In3Se3-phase-change resistor, which has much higher electrical resistivity than Ge2SbTe5 and of which electric resistivity can be varied by the factor of 105 times, related with the degree of crystallization. Due to its higher electrical resistivity, the switching power can be delivered more effectively. Since ln(2)Se(3) is single-phase binary compound, the device failure related to phase decomposition can be avoided. Since the volume of phase change is very limited, and the heating duration is only for few tens of nanoseconds to 10 mu s, the transition of ln(2)Se(3)-phase-change material is done under very far from its thermodynamic equilibrium condition, and thus, formation of the secondary phases or different crystalline phases was not observed. The static mode switching (dc test) is tested for the 5 mu m-sized In2Se3 PRAM device. In the first sweep, the as-grown amorphous In2Se3 resistor showed the high resistance state at low voltage region. However, when it reached the threshold voltage, the electrical resistance of the device was drastically reduced through the formation of an electrically conducting path. The pulsed mode switching of the 5 mu m-sized In2Se3 PRAM device shows that the reset (crystalline -> amorphous) of the device was done with a 70 ns-3.1 V pulse and the set (amorphous -> crystalline) of the device was done with a 10 mu s-1.2 V pulse. As high as 100 of switching dynamic range (ratio of R-high to R-low) was observed. (c) 2005 Elsevier B.V. All rights reserved.