1:30 PM - 3:30 PM
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[21p-PB3-5] Charge Trapping and Hysteresis Behavior in ReS2/SiO2 and ReS2/hBN
Field Effect Transistors
Keywords:hysteresis, charge trap, rhenium disulfide - hexagonal boron nitride
Rhenium disulfide (ReS2) based field-effect transistors (FETs) are of substantial interest in optoelectronic applications due to a direct band gap even in its multi-layers. Thin films of ReS2 are subject to the deterioration of charged impurities and traps in substrate similarly to other atomically-thin films, which cause severe degradation of FET characteristics such as carrier mobility, threshold voltage instability and hysteresis in I-V curves. In this work, we report the mitigation of such degradation in ReS2/SiO2 devices by substituting the substrate by a high-quality hexagonal boron nitride (hBN) insulating substrate which is atomically flat and free of charge trapping sites. Transistor characteristics were taken by two-terminal measurements with sweeping the bias of a back gate of a p-doped Si substrate. Carrier mobility of ReS2 channels showed an increase from 3.5 cm2/(Vs) (ReS2/SiO2) to 10.9 cm2/(Vs) (ReS2/hBN) due to the high quality of the hBN surface. Also, transfer characteristics exhibited a 70% reduction of hysteresis in Ids-Vg curves in ReS2/hBN device compared to the ReS2/SiO2 one. Since a single ReS2 flake was used in this experiment, the difference in the hysteresis is considered to be generated by the substrate underneath the ReS2 flake. From a comparison of the strength of hysteresis, the density of trapped charge is evaluated to be 9.7 x 1011 cm-2 and 4.1 x 1012 cm-2 in ReS2/hBN and ReS2/SiO2 devices, respectively, indicating the enhancement in the device quality by hBN. It will also be discussed on the impact of hBN substrate on the photoresponsivity for improving the photodetector device performance.