Use Of Phase Change Memory Research Articles

Addition of HfO2 interface layer for improved synaptic performance of phase change memory (PCM) devices

In this work, we will focus on the use of phase change memory (PCM) to emulate synaptic behavior in emerging neuromorphic system-architectures. In particular, we will show that the performance and energy-efficiency of large scale neuromorphic systems can be improved by engineering individual PCM devices used as synapses. This is obtained by adding a thin HfO2 interface layer to standard GST PCM devices, allowing for the lowering of the Set/Reset currents and the increase of the number of intermediate resistance states (or synaptic weights) in the synaptic potentiation characteristics. The experimentally obtained potentiation characteristics of such PCM devices are used to simulate a 2-layer ultra-dense spiking neural network (SNN) and to perform a complex visual pattern extraction from a test case based on real world data (i.e. cars passing on a 6-lane freeway). The total power dissipated in the learning mode, for the pattern extraction experiment is estimated to be as low as 60μW. Average detection rate of cars is found to be greater than 90%.

Pseudobinary Al2Te3-Sb2Te3 material for high speed phase change memory application

Al2Sb2Te6 is a pseudobinary material constructed by Sb2Te3 (fast crystallization speed but thermally unstable) and Al2Te3 (thermally stable but without memory switching ability). Al2Sb2Te6 material possesses advantages of these two binary compounds showing good memory switching ability with fast switching speed and good thermal stability. These improvements are believed to be closely related to the coordination situations of Al atoms in Al2Sb2Te6 material. Phase change memory device using Al2Sb2Te6 showed high speed (∼5 ns), low power consumption, and high endurance (∼106 cycles). Thus, we consider that Al2Sb2Te6 can be one of the most promising materials for phase change memory use.

Al1.3Sb3Te material for phase change memory application

Comparing with Ge2Sb2Te5, Al1.3Sb3Te is proved to be a promising candidate for phase-change memory use because of its higher crystallization temperature (∼210 °C), larger crystallization activation energy (3.32 eV), and better data retention ability (124 °C for 10 yr). Furthermore, Al1.3Sb3Te shows fast phase change speed and crystallizes into a uniformly embedded crystal structure. As short as 10 ns width, voltage pulse can realize reversible operations for Al1.3Sb3Te based phase-change memory cell. Moreover, phase-change memory cell based on Al1.3Sb3Te material also has good endurance (∼2.5 × 104 cycles) and an enough resistance ratio of ∼102.