Abstract
A two-dimension (2D) atomic-threshold-switching field-effect transistor (ATS-FET) was implemented, by connecting an AgTi/HfO2-based threshold-switching (TS) device in series to the drain electrode of the 2D baseline-FET with molybdenum disulfide (MoS2) channel material. We optimized/developed the Ag/HfO2-based TS device because its characteristic is associated to the way how to achieve high performance of the 2D ATS-FET. By reducing the effective device area of the Ag/HfO2-based TS device down to $4~\mu \text{m}^{2}$ , low threshold voltage ( $\text{V}_{\mathrm {T}} \sim 0.42$ V), low threshold current (IT, drain current at the threshold voltage, $\sim 3.79 \times 10^{-11}$ A), and low VT variation (~0.09 V) were achieved. This is because the randomly formed filaments and electric field are better controlled with the scaled effective area. Next, the titanium (Ti)-injection barrier layer was inserted between the top electrode and the switching layer, while maintaining the optimized area in the TS device. The inserted Ti-injection barrier layer prevents the migration of Ag ions into the switching layer, enabling the stable TS operation even under the compliance current of $100~\mu \text{A}$ . Additionally, it locally restricts the region where the filaments are created inside the switching layer, resulting in a 17% lower VT variation and stable IT to approximately $\sim 1.5 \times 10^{-11}$ A in 100 cycles. Due to the low off-state leakage current and low variation characteristic of the optimized AgTi/HfO2-based TS device, the 2D ATS-FET (vs. 2D baseline-FET) shows the reduction of off-state leakage current (by $\sim 10^{2}$ in sub-threshold region) and the stable switching characteristic. The proposed 2D ATS-FET shows stably steep switching characteristics, e.g., sub-threshold swing under forward bias (~19 mV/decade) and reverse bias (~26 mV/decade), because of its abruptly switching characteristics of the TS device.
Highlights
The power density of the state-of-the-art complementary metal oxide semiconductor (CMOS) devices in an integrated circuits has been increased for the past few decades, and it is one of the key factors in evaluating/ developing the integrated circuit devices
Compared with the VO2-based insulator-metal-transition device, the HfO2-based threshold switching (TS) device can contribute to suppress the off-state leakage current as well as to lower the operating voltage of 2D atomic-threshold-switching field-effect transistor (ATS-FET) because of its high off-state resistance (Roff ∼ 109 ) and low VT [19], [20]. This type of device has problems, i.e., VT variation, leakage issue due to the filament that is randomly formed in the switching layer of the TS device
The details of each parameter used in the ID equation above are as follows: i
Summary
The power density of the state-of-the-art complementary metal oxide semiconductor (CMOS) devices in an integrated circuits has been increased for the past few decades, and it is one of the key factors in evaluating/ developing the integrated circuit devices. Compared with the VO2-based insulator-metal-transition device, the HfO2-based TS device can contribute to suppress the off-state leakage current as well as to lower the operating voltage of 2D ATS-FET because of its high off-state resistance (Roff ∼ 109 ) and low VT [19], [20]. This type of device has problems, i.e., VT variation, leakage issue due to the filament that is randomly formed in the switching layer of the TS device. The off-state leakage current of proposed 2D ATS-FET (vs. 2D baseline-FET) was suppressed by ∼102 in the sub-threshold region and exhibited stable abrupt switching characteristics
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