MOCVD growth and properties of ultrawide bandgap MgSiN₂

Expanded from traditional group III-nitrides, group II-IV-N₂ provide opportunities to develop materials with new fundamental properties that may address challenges facing current device technologies based on pure III-nitrides. MgSiN₂ represents a new ultrawide bandgap semiconductor with a predicted energy bandgap of ~ 5.8 - 6.2 eV based on the first principle DFT calculations. The orthorhombic crystal structure of MgSiN₂ is compatible with the conventional wurtzite of III-nitrides. In this work, we demonstrated the MOCVD growth of MgSiN₂ thin films on GaN and sapphire substrates for the first time. The experimentally extracted optical bandgap of ~ 6.05±0.02 eV from absorption measurements agrees well with the theoretical predictions. Comprehensive material characterization was performed to correlate the MgSiN₂ crystalline quality with the MOCVD growth conditions. Effects on stoichiometry, crystallinity, and surface morphology were analyzed via SEM-EDS, XRD, high-resolution STEM, and AFM. Wet chemical etching studies on the MOCVD-grown MgSiN₂ films revealed excellent chemical stability when exposed to common chemicals utilized in typical fabrication processes. It was found that MgSiN₂ is wet-etchable using dilute hydrofluoric acid, a property unique among various UWBG semiconductors. Thus, MgSiN₂ represents a promising UWBG semiconductor that can bring unique properties compared to existing material platforms.