−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/Al
₂
O
₃
interface is quite continuous and atomically flat. A remarkably high threshold voltage (
${V}_{\text{TH}}$
) of −10 V and a maximum drain current density (
${I}_{D\_{}{\text{MAX}}}$
) of −156 mA/mm are simultaneously achieved in the fabricated devices. The devices with different source and drain (S/D) distances (
$L_{\text{SD}}$
) deliver robust
${V}_{\text{TH}}$
results and feature low OFF-state S/D leakage current
$\vert {I}_{\text{leakage}}\vert $
of ~
$6\times10$
⁻⁶
mA/mm at
${V}_{\text{GS}}$
= 0 V. The extracted field-effect mobility is as high as 127 cm
²
$\cdot \text{V}$
⁻¹
$\cdot \text{s}$
⁻¹
and the interface state density is as low as
$4.35\times10$
¹²
eV
⁻¹
$\cdot $
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.