In situ TEM study of phase transformation in oxide semiconductors

Ultra-wide bandgap oxide semiconductors are essential for advanced high-power electronics into the next generation. Despite their theoretical advantages over traditional semiconductors such as GaN and SiC, fully harnessing their potential is hindered by an insufficient understanding of critical material properties, particularly phase formation. One significant challenge is controlling the various polymorphs to create well-defined heterostructures with engineered properties. This review provides an overview of the capabilities and applications of in situ transmission electron microscopy (TEM) in semiconductor research, specifically addressing how it enables the study of phase transformations and charge distributions at the atomic level. We begin by introducing modern in situ TEM systems, detailing their advanced features and functionalities that enable real-time observation of dynamic processes at the nanoscale. Next, we explore the studies of phase transformations in Ga 2 O 3 and (Al x Ga 1-x ) 2 O 3 , with a particular focus on the pioneering work conducted by our group. These studies reveal critical insights into crystallization pathways, phase stability, and phase diagrams, highlighting the role of in-situ TEM in elucidating how these factors influence material properties. Finally, we offer perspectives on the future contributions of in situ TEM techniques, emphasizing their potential to drive semiconductor research forward through enhanced spatial and temporal resolution, improved environmental control, and novel analytical capabilities. This review aims to equip readers with a fundamental understanding of in situ TEM and inspire further advancements in the field of semiconductor materials. • Review on phase transformation in oxide semiconductor. • Ex-situ and in situ TEM studies in Ga 2 O 3 and (Al x Ga 1-x ) 2 O 3 are reviewed. • Offer insights into the crystallization pathway, phase stability, and phase diagram. • Discussion of in situ TEM sample preparation and AI-enabled microscopy data analysis.