Ultrafast phase change and long durability of BN-incorporated GeSbTe

Abstract

BN-incorporated amorphous Ge₂Sb₂Te₅ (GST) films were deposited by an ion beam sputtering deposition (IBSD) method using GST and BN targets. Based on in situ sheet resistance measurements, we confirmed that as the amount of BN increased, the crystallization temperature (T_c) increased from 150 °C to 260 °C. It was demonstrated that the phase change speed of BN-incorporated GST is ten times faster than that of GST using a nanosecond laser. By evaluating Johnson–Mehl–Avrami (JMA) plots and scanning electron microscopy (SEM) images, it was confirmed that the one-dimensional grain growth is dominant during the fast phase change of BN-incorporated GST because BN impurities can act like nuclei during the initial stage of crystal growth. After the 100 iteration test under rigorous acceleration conditions of SET/RESET switching using the pulsed laser system, it was confirmed that the void formation and thickness variation are very limited in the BN-incorporated GST, as compared to GST. This result originates from the low phase change stress of the BN-incorporated GST films during one-dimensional growth. The electrical SET speed and cyclability of the BN-incorporated GST device also improved significantly compared to GST.