-10 v Threshold Voltage High-Performance Normally-OFF C-Si Diamond MOSFET Formed by p⁺-Diamond-First and Silicon Molecular Beam Deposition Approaches

In this article, the normally- OFF oxidized Si-terminated (C-Si) diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) with as-deposited 0.5-nm silicon on diamond annealed at high temperature as the subsurface p-channel were presented for the first time. A novel method utilizing both a metal mask to realize the regrown heavily boron-doped (001) diamond layer first (p+-diamond-first) and a molecular beam deposition (MBD) method to procure atomic-scale silicon deposition was achieved. Scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDS) element mapping results suggest that the C-Si diamond/Al2O3 interface is quite continuous and atomically flat. A remarkably high threshold voltage (VTH) of -10 V and a maximum drain current density (IDMAX) of -156 mA/mm are simultaneously achieved in the fabricated devices. The devices with different source and drain (S/D) distances (LSD) deliver robust VTH results and feature low OFF-state S/D leakage current I leakage of 6×10 -6 mA/mm at V GS = 0 V. The extracted field-effect mobility is as high as 127 cm2 ċ V -1ċ s -1 and the interface state density is as low as 4.35×10 12 eV-1 ċ cm-2. These competitive results reveal that this first attempt of employing the combination of p+-diamond-first and MBD approaches promotes the integration of the advanced silicon manufacturing process with wide bandgap diamond material for power applications.