Device perspective of 2D materials beyond graphene

The rise of two-dimensional (2D) crystals has given new challenges and opportunities to the device research. The semiconducting MoS₂ as n-channel and few-layer phosphorene as p-channel have been considered as promising ultra-thin body channels for future microelectronic and optoelectronic devices. In this paper, we focus on the fundamental device properties in these 2D transistors. In the first part we introduce the dielectric integration on MoS₂ and other 2D crystals by atomic layer deposition, revealing the similarities and differences of dielectric integration on bulk and 2D crystals. Then we present the different metal contacts on MoS₂, showing Fermi level pinning at metal/2D interfaces. Through molecular chemical doping, contact resistance to MoS₂ is able to be reduced to 0.5 Ω·mm and high-performance MoS₂ FETs with drain current of 460 mA/mm are demonstrated. Then we discuss scaling of channel length and width of MoS₂ transistors. Finally we demonstrate a 2D CMOS inverter with a MoS₂ NFET and a few-layer phosphorene PFET, showing the potentials on these 2D crystals for heterogeneous device integrations.