[21p-PB3-1~5] 13.5 デバイス／集積化技術

▼ [21p-PB3-5] Charge Trapping and Hysteresis Behavior in ReS₂/SiO₂ and ReS₂/hBN
Field Effect Transistors

〇(D)Amir Zulkefli^1,2、Bablu Mukherjee¹、Kenji Watanabe¹、Takashi Taniguchi¹、Yutaka Wakayama^1,2、Shu Nakaharai¹ (1.National Inst. for Materials Science、2.Kyushu Univ.)

キーワード：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 I_ds-V_g 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.