Wafer-Scale Fabrication of Recessed-Channel PtSe2 MOSFETs With Low Contact Resistance and Improved Gate Control

Wafer-scale fabrication of PtSe₂ MOSFETs was demonstrated by photolithography on Pt films directly selenized at 400 °C. Taking advantage of the unique property of PtSe₂ to transition from a semiconductor to a semimetal as its thickness increases beyond a few monolayers, channel recess was adapted for improving gate control while keeping the contact resistance below 0.01 <inline-formula> <tex-math notation="LaTeX">$\Omega \cdot \text {cm}$ </tex-math></inline-formula>. The wafer-scale fabrication resulted in uniform device characteristics so that average instead of best results was reported. For example, the drain currents at <inline-formula> <tex-math notation="LaTeX">${V}_{\text {GS}} = -10$ </tex-math></inline-formula> V, <inline-formula> <tex-math notation="LaTeX">${V}_{\text {DS}} = -1$ </tex-math></inline-formula> V were <inline-formula> <tex-math notation="LaTeX">$25~\pm ~5$ </tex-math></inline-formula>, 57 ± 8, and <inline-formula> <tex-math notation="LaTeX">$618~\pm ~17~\mu \text{A}/\mu \text{m}$ </tex-math></inline-formula> for 4-, 8-, and 12-nm-thick PtSe₂, respectively. The corresponding peak transconductances were 0.20 ± 0.1, 0.60 ± 0.05, and <inline-formula> <tex-math notation="LaTeX">$1.4~\pm ~0.1~\mu \text{S}/\mu \text{m}$ </tex-math></inline-formula>. The forward-current cutoff frequency of 12-nm-thick PtSe₂ MOSFETs was 42 ± 5 MHz, whereas the corresponding frequency of maximum oscillation was 180 ± 30 MHz. These results confirmed the application potential of PtSe₂ for future-generation thin-film transistors.