Performance Enhancement of MOCVD Grown β-Ga2O3 MOSFETs on Silicon Substrates via AlN Buffer Layer

β-Ga2O3-based MOSFETs hold significant promise for high-power device applications due to their wide band gap and high breakdown voltage. However, the direct integration of β-Ga2O3 on silicon substrates is challenged by lattice and thermal expansion mismatches, which degrade device performance. This work explores the use of an aluminum nitride (AlN) buffer layer to mitigate these issues, offering improved structural quality and enhanced electrical performance. We demonstrate the growth of β-Ga2O3/AlN/Si films using metal–organic chemical vapor deposition, where the introduction of an AlN buffer layer significantly promotes the (−201) β-Ga2O3 orientation, which lacks in β-Ga2O3/Si films, as confirmed by XRD analysis. The presence of an AlN buffer layer is evidenced using SEM micrographs and XPS depth profile. The β-Ga2O3/AlN/Si MOSFETs exhibit a maximum drain current (IDS) of 52 mA/mm, remarkable drain current on/off ratio of ∼108 and a breakdown voltage (Vbr) of 178 V, surpassing the performance of β-Ga2O3/Si MOSFETs, which showed an IDS of 45 mA/mm and a Vbr of 106 V. These results underscore the potential of AlN buffer layers in advancing the performance and reliability of β-Ga2O3-based transistors on silicon, paving the way for next-generation power electronics.