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Start Over Author "Zhang, David" Journal ieee electron device letters
91 results on '"Zhang, David"'

7. Localized Thermal Effect Enhanced NBTI in Multifin pFinFETs Under Low Drain Bias

Author

Tang, Chengkang, Chen, Kun, Li, Xianghui, Chao, Xin, Li, Qingxuan, Wang, Chen, Zhu, Hao, Sun, Qingqing, and Zhang, David Wei

Abstract

In this letter, we present new observations on the degradation of negative bias temperature instability (NBTI) in multifin pFinFETs under low drain bias stress conditions. By analyzing changes in fin numbers, $\text{V}_{\text {gs}}$ stress, and $\text{V}_{\text {ds}}$ stress as well as conducting forward and reverse measurements, we inferred that thermal-induced threshold voltage degradation rather than single hot carrier degradation, is the primary driver of threshold voltage degradation. Experimental results from fast-pulsed drain bias experiments revealed an increase in threshold voltage degradation as the pulse width shortened in the sub-nanosecond range. This finding contrasts with the observation that threshold voltage degradation decreases as the frequency increases from DC to 1 GHz. The physical mechanisms underlying this degradation and the nonequilibrium carrier temperature dependence on sub-nanosecond drain pulses are analyzed. In addition, under different drain bias conditions, the equivalent temperature inside a device is estimated by extracting the activation energy of normal NBTI.

Published
2024
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8. Photoelectric Synaptic Device Based on Bilayerd OR/OP-InGaZnO for Neuromorphic Computing

Author

Song, Jieru, Meng, Jialin, Lu, Chen, Wang, Tianyu, Zhu, Hao, Sun, Qingqing, Zhang, David Wei, and Chen, Lin

Abstract

Photoelectric synaptic devices have exhibited remarkable potential in the field of neuromorphic computing (NC), facilitating high-speed and energy-efficient neuromorphic operations. Here, we explored the application of Indium-Gallium-Zinc-Oxide (IGZO) in two-terminal artificial synaptic devices for NC. The dielectric layer of the device, comprising an oxygen-rich layer and an oxygen-poor layer, effectively harnessed the migration of oxygen vacancies at their interface to exhibit memristive properties. The device emulated synaptic characteristics successfully under both electrical and optical stimuli, including excitatory post-synaptic current (EPSC), paired-pulse facilitation (PPF), long-term potentiation (LTP), and long-term depression (LTD). Furthermore, the recognition of handwritten digits was realized based on the synaptic weight resulting from light pulse stimulation, and the recognition rate was up to 92.6%. The results illustrated the advanced potential of IGZO-based memristors in NC.

Published
2024
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9. Oxygen Vacancy Modulation With TiO₂ Stack Interface Engineering for Ferroelectric Hf0.5Zr0.5O₂ Thin Films

Author

Wang, Xuepei, Wu, Maokun, Cui, Boyao, Li, Yuchun, Wu, Yishan, Wen, Yichen, Liu, Jinhao, Li, Xiaoxi, Ye, Sheng, Ren, Pengpeng, Ji, Zhigang, Lu, Hongliang, Zhang, David Wei, Wang, Runsheng, and Huang, Ru

Abstract

Since the discovery of ferroelectric switching in hafnium-based thin films, this family of materials has garnered significant attention. However, their higher coercive field not only constrains endurance performance but also escalates power consumption during polarization switching, rendering them incompatible with logic circuits. In this work, we have successfully reduced the coercive field of HZO ferroelectric thin films to 0.8 MV/cm by introducing TiO2 interface layers. When compared to HZO samples, the coercive field demonstrates a 30% reduction under the same electric field. Density functional theory (DFT) results support the phenomenon of interface oxygen injection by TiO2 interface layers. Further XPS and EDS physical characterizations reveal that TiO2 interfacial layers effectively diminishes the concentration of oxygen vacancies, thereby augmenting thin film ferroelectricity and device reliability.

Published
2024
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12. Back-End-of-Line Compatible HfO2/ZrO2 Superlattice Ferroelectric Capacitor with High Endurance and Remnant Polarization

Author

Cui, Boyao, primary, Wang, Xuepei, additional, Li, Yuchun, additional, Wu, Maokun, additional, Wu, Yishan, additional, Liu, Jinhao, additional, Li, Xiaoxi, additional, Ren, Pengpeng, additional, Ye, Sheng, additional, Ji, Zhigang, additional, Lu, Hongliang, additional, Wang, Runsheng, additional, Zhang, David Wei, additional, and Huang, Ru, additional

Published
2023
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16. Oxygen Vacancy Modulation with TiO2 Stack Interface Engineering for Ferroelectric Hf0.5Zr0.5O2 Thin Films

Author

Wang, Xuepei, primary, Wu, Maokun, additional, Cui, Boyao, additional, Li, Yuchun, additional, Wu, Yishan, additional, Wen, Yichen, additional, Liu, Jinhao, additional, Li, Xiaoxi, additional, Ye, Sheng, additional, Ren, Pengpeng, additional, Ji, Zhigang, additional, Lu, Hongliang, additional, Zhang, David Wei, additional, Wang, Runsheng, additional, and Huang, Ru, additional

Published
2023
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25. Demonstration of Robust Breakdown Reliability and Enhanced Endurance in Gallium Doped HfO2 Ferroelectric Thin Films

Author

Huang, Teng, Li, Yu-Chun, Chen, Chu-Fan, Li, Xiao-Xi, Gu, Ze-Yu, Zhang, David Wei, Zhu, Xiao-Na, and Lu, Hong-Liang

Abstract

In this letter, gallium doped HfO2(Ga:HfO $_{{2}}{)}$ ferroelectric capacitors were fabricated and characterized. It is demonstrated that the W/Ga:HfO2/W capacitors under 650 °C rapid thermal annealing achieved a comprehensively good ferroelectricity, including a large remnant polarization ( $2{P}_{\text {r}}{)}$ of $32.0~\mu \text{C}$ /cm2 and a small coercive electric field ( ${E}_{\text {c}}{)}$ of 0.9 MV/cm. Moreover, the devices exhibit robust breakdown reliability including high breakdown electric field ( ${E}_{\text {BD}}{)}$ (>4.5 MV/cm), and large breakdown voltage (>2.7 V) for 10-year time-dependent dielectric breakdown (TDDB) lifetime. Moreover, the robust endurance ( $10^{{10}}{)}$ was achieved in W/Ga:HfO2/W capacitors under 1 MHz loading. Such improvements were mainly attributed to the decreased ${E}_{\text {c}}/{E}_{\text {BD}}$ ratio from Ga effectively doping, which lowered the probability of breakdown during cycling. This work provides the perspective to optimize the reliability HfO2-based ferroelectric devices through doping engineering.

Published
2023
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29. The ID Instability Induced by Reverse Conduction Stress in p-GaN Gate HEMTs

Author

Chao, Xin, Wang, Luyu, Li, Xianghui, Tang, Chengkang, Chen, Lin, Wang, Chen, Zhu, Hao, Sun, Qingqing, and Zhang, David Wei

Abstract

In this work, the impact of reverse conduction stress on the output current ( ${I} _{D}$ ) instability in p-GaN gate HEMT are investigated. With more negative drain stress ( ${V} _{\text {DS}, \text {str}}$ below −5 V), the ${I} _{D, \text {max}}$ shows a positive shift in the ${I} _{D} - {V}_{\text {DS}}$ measurement at ${V} _{\text {GS}}$ = 3 V and a negligible change at ${V} _{\text {GS}}$ = 5 V, meanwhile the ${V} _{\text {TH}}$ shows a negative shift after the stress. By contrast, the ${I} _{D, \text {max}}$ is basically unchanged with the ${V} _{\text {DS}, \text {str}}$ above −5 V. Through the simulation and extended experiments, it is found that the hole tunneling under the more negative ${V} _{\text {DS}, \text {str}}$ and the subsequent hole accumulation and trapping within the gate stack dominate the ${I} _{D, \text {max}}$ instability. The comparison of gate leakage and the transmission electron microscopy (TEM) observation before and after the stress further shows that the gate stack degenerates.

Published
2023
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34. Improved Ferroelectricity and Tunneling Electro Resistance in Zr-Rich HfxZr1-xO2 Ferroelectric Tunnel Junction

Author

Yu, Jiajie, Wang, Tianyu, Li, Zhenhai, Liu, Yongkai, Meng, Jialin, Xu, Kangli, Liu, Pei, Zhu, Hao, Sun, Qingqing, Zhang, David Wei, and Chen, Lin

Abstract

HfO2 based ferroelectric materials have great application potential in ferroelectric tunneling junction. Here, the low temperature annealed Zr-Rich HfxZr $1_{-\text {x}}\text{O}_{{2}}$ films based ferroelectric tunnel junction is fabricated on a silicon substrate. It is found that ferroelectricity of the film under operating voltages of 3.3V, 3.5V and 3.7V are excellent, where the largest residual polarization 2Pr is above 50 $\mu \text{C}$ /cm2. The excellent ferroelectricity enables the device to operate at an extremely high speed of 50ns and achieve a high tunneling electro resistance ratio (>50). Based on the first principal calculation, we found that Zr-Rich HfxZr1-xO2 films will show more O-phase and less T-phase. This research paves the pathway to improve the performance of the HfO2 based ferroelectric tunneling junction for future ferroelectric application.

Published
2023
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35. Back-End-of-Line Compatible HfO2/ZrO2 Superlattice Ferroelectric Capacitor With High Endurance and Remnant Polarization

Author

Cui, Boyao, Wang, Xuepei, Li, Yuchun, Wu, Maokun, Wu, Yishan, Liu, Jinhao, Li, Xiaoxi, Ren, Pengpeng, Ye, Sheng, Ji, Zhigang, Lu, Hongliang, Wang, Runsheng, Zhang, David Wei, and Huang, Ru

Abstract

The hafnium-zirconium oxide (HZO) has been reported to be a promising candidate for low-power VLSI logic and memory applications. However, the demand for high processing temperatures above 500 °C keeps it away from the Back-End-of-Line (BEOL) process. Many reports have explored various methods to facilitate the formation of orthorhombic phases at lower temperatures, but these methods have typically resulted in low remnant polarization ( ${P}\text{r}$ ) and poor reliability due to poor crystallinity and oxygen vacancy (Ov) accumulation. To address these challenges, we have chosen tungsten (W) as the capping electrode due to its superior capability for inducing orthorhombic phases. We have also replaced the conventional HZO layer with a stacked HfO2-ZrO2 superlattice with optimized Ov distribution and improved crystallinity. As a result, our sample processed at 400 °C exhibits a maximum $2{P}\text{r}$ of $32 ~\mu \text{C}$ /cm2 at 2.5 MV/cm. It demonstrates the stable endurance cycles up to ${2} \times {10} ^{{9}}$ exceeding the performance of the W-HZO control sample and remaining competitive with the most recent results in the literature.

Published
2023
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37. Ultralow-Power Synaptic Transistor Based on Wafer-Scale MoS 2 Thin Film for Neuromorphic Application.

Author

Wang, Chen, Liu, Hao, Chen, Lin, Zhu, Hao, Ji, Li, Sun, Qing-Qing, and Zhang, David Wei

Subjects
THIN films, THIN film transistors, NANOELECTRONICS, TRANSISTORS, LONG-term potentiation, POSTSYNAPTIC potential, ATOMIC layer deposition
Abstract

In the next-generation computing framework, synaptic devices modulated using analogue weight storage are expected with capability of performing neuromorphic computing tasks. Recently, 2D transition metal dichalcogenides (TMDCs) based solid-state devices have demonstrated excellent electrical performance showing great potential in nanoscale synaptic electronics. In this letter, artificial synaptic transistors are proposed and fabricated on the atomic layer deposited 2D MoS2 thin film with an integrated high-k dielectric gate stack. The synapse cells can simulate fundamental synaptic functions similar to those of biological synapses, such as long-term potentiation and depression. Moreover, the ultralow power consumption shows that the proposed synapse is more efficient than most three-terminal synaptic transistors. We also emulate a multi-synapse network to demonstrate intrinsic heterogeneity in biological brain. The experimental results have validated the feasibility of synaptic devices based on 2D TMDCs and have contributed a promising approach to the development of the next-generation brain-like neuromorphic systems. [ABSTRACT FROM AUTHOR]

Published
2021
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50. Effects of the Variation of V\text {GS} Sweep Range on the Performance of Negative Capacitance FETs.

Author

Zhou, Jiuren, Han, Genquan, Li, Jing, Liu, Yan, Peng, Yue, Zhang, Jincheng, Sun, Qing-Qing, Zhang, David Wei, and Hao, Yue

Subjects
FIELD-effect transistors, ELECTRIC capacity, ELECTRIC potential
Abstract

We report the first investigation of the impacts of gate voltage sweep range V\text {GS,range} on the performance of negative capacitance (NC) transistors. As V\text {GS,range} is reduced, NC GeSn pFETs generally exhibit an increased hysteresis or a transition from non-hysteretic to hysteretic, and show a degradation of I\text {DS} . This is due to the reduction of the ratio of remnant polarization P\text {r} to coercive field E\text {c} with the reduced voltage across the HZO. Interestingly, however, some NC devices show a negligible impact of V\text {GS,range} on hysteresis and I\text {DS} . The NC transistor demonstrates a stable hysteresis in 139–149 mV range and the improved SS and I\text {DS} over the control device, with a reduced V\text {GS,range} of 0.5 to −0.5 V. To obtain device performance independent of V\text {GS,range} , the ratio of P\text {r}/{E}\text {c} of the HZO needs to stabilize in a very small V\text {GS,range} . [ABSTRACT FROM AUTHOR]

Published
2018
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