Reduction of Threshold Voltage Hysteresis of MoS2 Transistors with 3-Aminopropyltriethoxysilane Passivation and Its Application for Improved Synaptic Behavior

Although molybdenum disulfide (MoS2) is highlighted as a promising channel material, MoS2 -based field-effect transistors (FETs) have a large threshold voltage hysteresis (Delta V-TH) from interface traps at their gate interfaces. In this work, the Delta V-TH of MoS2 FETs is significantly reduced by inserting a 3-aminopropyltriethoxysilane (APTES) passivation layer at the MoS2/SiO2 gate interface owing to passivation of the interface traps. The Delta V-TH is reduced from 23 to 10.8 V by inserting the 1%-APTES passivation layers because APTES passivation prevents trapping and detrapping of electrons, which are the major source of the Delta V-TH. The reduction in the density of interface traps (D-it) is confirmed by the improvement of the subthreshold swing (SS) after inserting the APTES layer. Furthermore, the improvement in the synaptic characteristics of the MoS2 FET through the APTES passivation is investigated. Both inhibitory and excitatory postsynaptic currents (PSC) are increased by 33% owing to the reduction in the Delta V-TH and the n-type doping effect of the APTES layer; moreover, the linearity of PSC characteristics is significantly improved because the reduction in Delta V-TH enables the synaptic operation to be over the threshold region, which is linear. The application of the APTES gate passivation technique to MoS2 FETs is promising for reliable and accurate synaptic applications in neuromorphic computing technology as well as for the next-generation complementary logic applications.