Revealing the Impact of Prestructural Ordering in GaSb Thin Films
Résumé
For phase change materials (PCMs) to become a viable universal memory candidate and obsolete von-Neumann architecture, materials with very low crystallization speed are needed. Moreover, introducing pre-structural ordering inside the material is also being touted as one of the promising techniques to reach the speed of SRAM or further down. In this aspect, GaSb alloys are showing much promise for not only having very low crystallization times by themselves and also showing an enormous drop in the programming time while crystallizing the re-amorphized material. Here we demonstrate how the threshold switching behaviour changes for the fully amorphous film in contrast with the disordered film with nucleation sites using conductive-Atomic Force Microscopy. It is found that the required power and programming current for memory switching with nominally stoichiometric GaSb (44:56) are 23 nW and 6.2 nA, respectively. As expected for a nucleation oriented PCM, the deposited thin film has two voltage thresholds during the local programming process, one for conduction and another for memory switching. However, when the nucleation sites are introduced inside the disordered film, the conduction and memory switching become simultaneous. This is also found to be reducing threshold power and SET current by 93% (1.5 nW) and 91% (550 pA), respectively. Furthermore, we also reveal the origin behind this behavioural change observed between these two thin films by using high-resolution transmission electron microscopy and synchrotron radiation photoelectron spectroscopy.
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