Origin of interfacial charges of Al2O3/Si and Al2O3/GaN heterogeneous heterostructures

Schematic of the Al2O3/GaN and Al2O3/Si H2s. [Display omitted] •In this study, the nonstoichiometric atomic ratios of O to Al from the bulk Al2O3 found at the interfaces of Al2O3/Si and Al2O3/GaN H2s were correlated with the interfacial charge polarity. The different charge polarity at the interfaces of Al2O3/GaN and Al2O3/Si H2s strongly suggests that the observed charges are not intrinsic to Al2O3; instead, they can be determined by the underlying semiconductor substrates on which Al2O3 is deposited. The study provide a deep understanding on the origin of interfacial charges at the insulator-semiconductor interfaces. Al2O3 is a broadly employed dielectric and significant interfacial charges occur at Al2O3/semiconductor interfaces. However, the charge origin is often unclear that severely impacts device engineering and design. Al2O3/Si and Al2O3/GaN are two of the most common heterogeneous heterostructures (H2s) for many crucial devices including GaN transistors and Si solar cells. While negative charges are extensively observed in Al2O3/Si, positive charges exist in Al2O3/GaN, both of which are not well understood. In this study, we performed in-depth interfacial studies of the Al2O3/Si and Al2O3/GaN H2s to clarify the origin of the interfacial charges. Stoichiometry deviations were found at the interfaces of the two H2s where Al surpasses O for Al2O3/GaN, whereas O dominates at the Al2O3/Si interface. Therefore, we propose that the different interfacial charges are caused by nonstoichiometry atomic ratios of Al2O3 at the interface. The study indicates the important role of the semiconductor surface on the device performance, provide a deep understanding on the origin of interfacial charges at the insulator-semiconductor interfaces.