All CVD Boron Nitride Encapsulated Graphene FETs With CMOS Compatible Metal Edge Contacts

We report on the fabrication and characterization of field-effect transistors (FETs) based on chemical vapor deposited (CVD) graphene encapsulated between few layer CVD boron nitride (BN) sheets with complementary metal–oxide–semiconductor (CMOS) compatible nickel edge contacts. Noncontact terahertz time-domain spectroscopy (THz-TDS) of large-area BN/graphene/ BN (BN/G/BN) stacks reveals average sheet conductivity >1 mS/sq. and average mobility of 2500 cm2/V $\cdot $ s. Improved output conductance is observed in dc measurements under ambient conditions, indicating the potential for radio frequency (RF) applications. Moreover, we report a maximum voltage gain of 6 dB from a low-frequency signal amplifier circuit. RF characterization of the GFETs yields an ${f}_{T}\times {L}_{g}$ product of 2.64 GHz $\cdot ~\mu \text{m}$ and an ${f}_{{\textsf {Max}}}\times {L}_{g}$ product of 5.88 GHz $\cdot ~\mu \text{m}$ . This paper presents for the first time THz-TDS usage in combination with other characterization methods for device performance assessment on BN/G/BN stacks. The results serve as a step toward scalable, all CVD 2-D material-based FETs for CMOS compatible future nanoelectronic circuit architectures.