High-Performance H-Diamond MOSFETs With HAO as Gate Dielectrics

This work presents the design and characterization of high-performance hydrogen-terminated diamond (H-diamond) MOSFETs utilizing Al-doped HfO2 (HAO) as the gate dielectric. A 15-nm HAO layer with a Hf-to-Al ratio of 16:1 was deposited at 250 °C on a single-crystal diamond substrate, achieving a dielectric constant of 20.2 and a gate oxide capacitance (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit {C}_{\text {ox}}$ </tex-math></inline-formula>) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.19 \; \mu $ </tex-math></inline-formula>F/cm2. Two MOSFETs were fabricated and evaluated: one with a gate length of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.8 \; \mu $ </tex-math></inline-formula>m and a channel length of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$13 \; \mu $ </tex-math></inline-formula>m and another with a gate length of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.4 \; \mu $ </tex-math></inline-formula>m and a channel length of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10 \; \mu $ </tex-math></inline-formula>m. The devices exhibit a high breakdown electric field of 14.33 MV/cm and a low gate leakage current density (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit {J}_{\textit {G}}$ </tex-math></inline-formula>) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.57 \times $ </tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-7}$ </tex-math></inline-formula> A/cm2 at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit {V}_{\text {GS}}$ </tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ = -5$ </tex-math></inline-formula> V, indicating ultralow gate leakage during operation. The output characteristics show a high <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on/off</small> switching ratio of approximately 108 across a 3.5-V gate voltage swing, making these devices attractive for practical applications.