Performance tunability of field-effect transistors using MoS 2(1-x) Se 2x alloys

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, MoS1Se1and 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 SiO2and high-k HfO2as gate dielectrics, and show tunability in threshold voltage, subthreshold slope, drain current, and mobility. MoS1Se1shows better promise for low-power FETs with a minimum subthreshold slope of 70 mV/dec, whereas MoS0.4Se1.6, with its higher mobility, is suitable for faster operations. Using HfO2as gate dielectric, there is an order of magnitude reduction in interface traps and 2x improvement in mobility and drain current, compared to SiO2. In contrast to MoS2, the FETs on HfO2also display enhancement-mode operation, making them better suited for CMOS applications.