2D-Material Based p-Type Vertical FETs Realized by Using Metallic TMDs as an Electrical Contact

2D-material based p-type semiconductors, which are inevitable components of CMOS technology, have been bottlenecked in realizing their desired performances despite researchers’ extensive studies on electrical contacts formed by using traditional metals. In this regard, developing advanced-structured devices, including vertical Field-Effect-Transistors (FETs), has predominantly progressed for n-type semiconductors. Here, we demonstrate van-der-Waals metallic contacts utilizing atomically thin 2D metals of TaS₂, NbSe₂, and NbS₂ having high work functions in the range of 4.8 to 5.9 eV which are favorable for forming p-type ohmic contact to WSe₂ while suppressing Fermi-level-pinning induced mainly due to the direct deposition process. We found that NbSe₂-contacted WSe₂ semiconductor devices show a reliably high on-current of ~10⁴ A/μm with p-type ohmic contact properties. Moreover, we demonstrate the fabrication of p-type vertical FETs realized by using 2D metals with a high on-off ratio of ~10⁵. We, further, demonstrate a vertical pseudo-CMOS based on 2D metals which can significantly reduce channel length of FETs.