| 초록 |
The material properties of Bi2Te3 doped Ge2Sb2Te5 (GST-Bi) thin films were characterized for the phase change random access memory (PRAM) application. The as-deposited Bi2Te3 films had very higher crystallinity and lower electrical resistivity than GeTe, Sb2Te3 and Ge2Sb2Te5 (GST) films. The electrical resistivity of the as-deposited GST-Bi films was lower than that of the undoped GST film. After the isochronal annealing during 10 sec, however, both of GST and GSB-Bi thin films had the almost similar electrical resistivity. The transient SET-RESET switching results confirmed that the resistance ratio of the GST-Bi was about a hundred times and, hence it could offer a sufficient data sensing margin for PRAM application. Besides, the RESET programming pulse voltage of the GST-Bi was 30 % lower than that of the undoped GST. From the resistance-voltage (R-V) curve, three important facts were observed. First of all, the minimum voltage to obtain a highly resistive RESET state was 1.3V for GST-Bi with Bi2Te3 power of 2.5W. This value was about 30% smaller than the minimum voltage of GST, 2.0V. Secondly, both SET and RESET state of GST-Bi have a lower resistance value than those of GST. This can enhance the overall device speed because it has been known that the lower SET resistance, the faster data reading speed. Finally, in spite of the Bi2Te3 doping, the resistance ratio of GST-Bi was maintained about a hundred times and this is enough for a stable data sensing for the PRAM Application. In addition, GST-Bi exhibited a good endurance property with the repetitive write and erase operation up to 1000 cycles. Therefore, the GST-Bi could be a promising material for the high density PRAM fabrication. |
