Correlative Atomic Coordination and Interfacial Charge Polarity in Al₂O₃/GaN and Al₂O₃/Si Heterostructures

Al₂O₃ is used to form Al₂O₃/GaN and Al₂O₃/Si heterostructures for many electronic and optoelectronic devices. Yet the origins of the positive interfacial charges in the Al₂O₃/GaN heterostructure and negative interfacial charges in the Al₂O₃/Si heterostructure are often elusive. Herein, in-depth studies of the Al₂O₃/GaN and Al₂O₃/Si heterostructures are conducted, especially on how the atomic coordination structure affects the interfacial charges. It is discovered that the octahedral [AlO₆]⁹⁻ coordination surpassed tetrahedral [AlO₄]⁵⁻ coordination at the Al₂O₃/GaN interface, whereas tetrahedral [AlO₄]⁵⁻ coordination dominated at the Al₂O₃/Si interface. Therefore, the interfacial charge polarity is correlated with the nonstoichiometry atomic coordination of Al₂O₃ at the two interfaces. This study reveals the atomic origin of charge polarity at high-k/semiconductor interfaces and could facilitate the development of high-performance optoelectronic and electronic devices through engineering the atomic coordination structure of the high-k materials.