Performance tunability of field-effect transistors using MoS_2(1-x)Se_2xalloys

Ultra-thin channel materials with excellent tunability of their electronic properties are necessary for the scaling of electronic devices. Two-dimensional materials such as transition metal dichalcogenides (TMDs) are ideal candidates for this due to their layered nature and great electrostatic control. Ternary alloys of these TMDs show composition-dependent electronic structure, promising excellent tunability of their properties. Here, we systematically compare molybdenum sulphoselenide (MoS2(1-x)Se2x) alloys, MoS1Se1 and MoS0.4Se1.6. We observe variations in strain and carrier concentration with their composition. Using them, we demonstrate n-channel field-effect transistors (FETs) with SiO2 and high-k HfO2 as gate dielectrics, and show tunability in threshold voltage, subthreshold slope (SS), drain current, and mobility. MoS1Se1 shows better promise for low-power FETs with a minimum SS of 70 mV dec-1, whereas MoS0.4Se1.6, with its higher mobility, is suitable for faster operations. Using HfO2 as gate dielectric, there is an order of magnitude reduction in interface traps and 2× improvement in mobility and drain current, compared to SiO2. In contrast to MoS2, the FETs on HfO2 also display enhancement-mode operation, making them better suited for CMOS applications.