Ab Initio Insights into the Reactivity of Precursors in Atomic Layer Deposition: A Case Study of GeAsSe

Ternary GeAsSe alloys that exhibit Ovonic Threshold Switching are promising selector materials for memory arrays. This application requires conformal deposition of GeAsSe films with good composition control on high-aspect-ratio structures, preferably by Atomic Layer Deposition (ALD). However, there are currently no GeAsSe ALD processes reported in literature. Reactive precursors should, therefore, be identified─a challenging task for ternary materials due to the numerous precursor combinations. In this work, we reveal favorable and unfavorable precursor combinations by computing the precursor gas-phase reaction energies using ab initio simulations. The results are consistent with experiments, as demonstrated ALD processes show exoenergetic reactions. Favorable additional chemistries are silylation, alkylation, and hydrogen transfer, irrespective of the central element (Ge, As, and Se), which provides promising pathways to enable GeAsSe ALD. Selenium coreactants show similar reactivity with germanium and arsenic precursors, implying that demonstrated GeSe ALD precursor chemistries can also be used for As2Se3 ALD. The presented insights into precursor reactivity and ligand reactivity trends may advance the development of deposition processes for novel thin films, including GeAsSe, using ALD, chemical vapor deposition, or area-selective deposition.