Computational and experimental studies on band alignment of ZnO/InxGa2-xO3/GaN heterojunctions

The ZnO/GaN heterojunctions are extensively investigated now, owing to their good luminescent properties and devisable capability to form efficient hybrid structures. An electron-blocking layer inserted into heterojunctions can greatly change their properties. In this work, n-ZnO/beta-InxGa(2-x)O(3)/p-GaN heterojunctions have been successfully formed using atomic layer deposition methods. We show that the doping of In can effectively tune the band edges of the heterojunctions. First-principle calculations reveal that the bandgap of bulk beta-InxGa(2-x)O(3) shrinks linearly with the increase in In contents, accompanied by an upward movement of the valence band maximum and a downward movement of the conduction band minimum. As the indium concentrations increase, the valence band offsets show an upward movement at both the InxGa(2-x)O(3)/GaN and ZnO/InxGa(2-x)O(3) interfaces, while the conduction band offsets present different trends. A broad, reddish yellow-green emission appears after In doping, which verifies the effect of band alignment. What is more, we show that the amorphization of InxGa(2-x)O(3) can play an important role in tuning the band edge. This work provides access to a series of band offsets tunable heterojunctions and can be used for the further design of direct white light-emitting diodes without any phosphors, based on this structure.

Automated summary

In this study, n-ZnO/beta-InxGa(2-x)O(3)/p-GaN heterojunctions were successfully fabricated using atomic layer deposition methods, and it was demonstrated that the band edges of the heterojunctions can be effectively tuned by In doping. First-principle calculations revealed that with increasing In contents, the bandgap of β-InxGa(2-x)O(3) decreased linearly, accompanied by movements of the valence band maximum and the conduction band minimum. In doping induced a broad, reddish yellow-green emission, confirming the effect of band alignment. This work provides a pathway to tunable heterojunctions with adjustable band offsets, which can be employed for the further development of direct white light-emitting diodes without phosphors.