Reduction of write current with improved thermal stability in GeSe₂ doped Sb₂Te₃ films for phase change memory applications

Abstract

Chalcogenide alloy-based semiconductors have gained significant attention in recent decades due to its applications in phase change memory (PCM). Sb2Te3 has proven to be an alternative to Static and Dynamic Random Access Memory and can be a suitable candidate for commercial memory devices due to their fast switching speed. However, Sb2Te3 suffers from low amorphous phase stability and high RESET current, which needs further improvement for high power efficiency. In this work, we have prepared (Sb2Te3)1−x (GeSe2) x (x = 0.06, 0.12, 0.18, 0.24, 0.3) films to investigate their PCM properties. The films showed a rise in transition temperature to transform from high resistive amorphous (RESET) to low resistive crystalline (SET) states with doping that leads to significant enhancement in amorphous phase stability. For 30% doping of GeSe2 in Sb2Te3, the data retention temperature increases from 20.2 °C to 84.6 °C, and the resistance contrast also increases from 102 to 105. The rise in electrical resistance with doping in the amorphous as well as crystalline states leads to a drop in threshold current (I th) from 3.5 to 0.8 mA. This also reduces the RESET and SET currents. By analyzing the samples using finite element method, it was found out that the high resistance materials produce more heat, resulting in a lower write current in an energy efficient PCM device.