More Like this

1. High performance AlGaN/GaN MISHEMTs using N ₂ O treated TiO ₂ as the gate dielectric

   https://doi.org/10.1088/1361-6641/ad96dc  

   Zhama, Tuofu; Cui, Peng; Chen, Zijun; Zhang, Jie; Zhao, Haochen; Wei, Lincheng; Sharma, Ashwani; Bakaul, Saidur; Zeng, Yuping (December 2024, Semiconductor Science and Technology)

   Abstract In this work, TiO₂thin films deposited by the atomic layer deposition (ALD) method were treated with a special N₂O plasma surface treatment and used as the gate dielectric for AlGaN/GaN metal insulator semiconductor high electron mobility transistors (MISHEMTs). The N₂O plasma surface treatment effectively reduces defects in the oxide during low-temperature ALD growth. In addition, it allows oxygen atoms to diffuse into the device cap layer to increase the barrier height and thus reduce the gate leakage current. These TiO₂films exhibit a dielectric constant of 54.8 and a two-terminal current of 1.96 × 10⁻¹⁰A mm⁻¹in 2μm distance. When applied as the gate dielectric, the AlGaN/GaN MISHEMT with a 2μm-gate-length shows a high on/off ratio of 2.59 × 10⁸and a low subthreshold slope (SS) of 84 mV dec⁻¹among all GaN MISHEMTs using TiO₂as the gate dielectric. This work provides a feasible way to significantly improve the TiO₂film electrical property for gate dielectrics, and it suggests that the developed TiO₂dielectric is a promising high-κgate oxide and a potential passivation layer for GaN-based MISHEMTs, which can be further extended to other transistors. 

   more » « less
2. Temperature-Dependent Characteristics and Electrostatic Threshold Voltage Tuning of Accumulated Body MOSFETs

   https://doi.org/10.1109/TED.2022.3184906  

   Talukder, A. B.; Smith, Brittany; Akbulut, Mustafa; Dirisaglik, Faruk; Silva, Helena; Gokirmak, Ali (June 2022, IEEE Transactions on Electron Devices)

   Narrow-channel accumulated body nMOSFET devices with p-type side gates surrounding the active area have been electrically characterized between 100 and 400 K with varied side-gate biasing ( Vside ). The subthreshold slope (SS) and drain induced barrier lowering (DIBL) decrease and threshold voltage ( Vt ) increases linearly with reduced temperature and reduced side-gate bias. Detailed analysis on a 27 nm × 78 nm (width × length) device shows SS decreasing from 115 mV/dec at 400 K to 90 mV/dec at 300 K and down to 36 mV/dec at 100 K, DIBL decreasing by approximately 10 mV/V for each 100 K reduction in operating temperature, and Vt increasing from 0.42 to 0.61 V as the temperature is reduced from 400 to 100 K. Vt can be adjusted from ∼ 0.3 to ∼ 1.1 V with ∼ 0.3 V/V sensitivity by depletion or accumulation of the body of the device using Vside . This high level of tunability allows electronic control of Vt and drive current for variable temperature operation in a wide temperature range with extremely low leakage currents ( < 10 −13 A). 

   more » « less
3. High- κ polymers of intrinsic microporosity: a new class of high temperature and low loss dielectrics for printed electronics

   https://doi.org/10.1039/C9MH01261C  

   Zhang, Zhongbo; Zheng, Jifu; Premasiri, Kasun; Kwok, Man-Hin; Li, Qiong; Li, Ruipeng; Zhang, Suobo; Litt, Morton H.; Gao, Xuan P.; Zhu, Lei (February 2020, Materials Horizons)

   High performance polymer dielectrics are a key component for printed electronics. In this work, organo-soluble polymers of intrinsic microporosity (PIMs) are reported for the first time to demonstrate desirable dielectric properties with a high permittivity (or κ ), heat resistance, and low dielectric loss simultaneously. Due to the highly dipolar sulfonyl side groups (4.5 D) and rigid contorted polymer backbone, a sulfonylated PIM (SO 2 -PIM) enabled friction-free rotation of sulfonyl dipoles in the nanopores. As such, an optimal balance between relatively high κ and low dielectric loss is achieved in a broad temperature window (−50–200 °C). For example, the discharged energy density reached 17 J cm −3 with κ = 6.0. The discharge efficiency was 94% at 150 °C/300 MV m −1 and 88% at 200 °C/200 MV m −1 . Furthermore, its application as a high- κ gate dielectric in field effect transistors (FETs) is demonstrated. With the bilayer SO 2 -PIM/SiO 2 gate dielectric, InSe FETs exhibited a high electron mobility in the range of 200–400 cm 2 V −1 s −1 , as compared to 40 cm 2 V −1 s −1 for the bare SiO 2 -gated InSe FET. This study indicates that highly dipolar PIMs with a rigid polymer backbone and large free volume are promising as next generation gate dielectric materials for printed electronics. 

   more » « less
4. Temperature dependent characteristics of β -Ga2O3 FinFETs by MacEtch

   https://doi.org/10.1063/5.0159420  

   Ren, Zhongjie; Huang, Hsien-Chih; Lee, Hanwool; Chan, Clarence; Roberts, Henry C.; Wu, Xihang; Waseem, Aadil; Bhuiyan, A F; Zhao, Hongping; Zhu, Wenjuan; et al (July 2023, Applied Physics Letters)

   Understanding the thermal stability and degradation mechanism of β-Ga2O3 metal-oxide-semiconductor field-effect transistors (MOSFETs) is crucial for their high-power electronics applications. This work examines the high temperature performance of the junctionless lateral β-Ga2O3 FinFET grown on a native β-Ga2O3 substrate, fabricated by metal-assisted chemical etching with Al2O3 gate oxide and Ti/Au gate metal. The thermal exposure effect on threshold voltage (Vth), subthreshold swing (SS), hysteresis, and specific on-resistance (Ron,sp), as a function of temperature up to 298 °C, is measured and analyzed. SS and Ron,sp increased with increasing temperatures, similar to the planar MOSFETs, while a more severe negative shift of Vth was observed for the high aspect-ratio FinFETs here. Despite employing a much thicker epilayer (∼2 μm) for the channel, the high temperature performance of Ion/Ioff ratios and SS of the FinFET in this work remains comparable to that of the planar β-Ga2O3 MOSFETs reported using epilayers ∼10–30× thinner. This work paves the way for further investigation into the stability and promise of β-Ga2O3 FinFETs compared to their planar counterparts. 

   more » « less
5. Demonstration of Wide Bandgap AlGaN/GaN Negative‐Capacitance High‐Electron‐Mobility Transistors (NC‐HEMTs) Using Barium Titanate Ferroelectric Gates

   https://doi.org/10.1002/aelm.202000074  

   Chandrasekar, Hareesh; Razzak, Towhidur; Wang, Caiyu; Reyes, Zeltzin; Majumdar, Kausik; Rajan, Siddharth (July 2020, Advanced Electronic Materials)

   Abstract A negative‐capacitance high electron mobility transistor (NC‐HEMT) with low hysteresis in the subthreshold region is demonstrated in the wide bandgap AlGaN/GaN material system using sputtered BaTiO₃as a “weak” ferroelectric gate in conjunction with a conventional SiN_xdielectric. An enhancement in the capacitance for BaTiO₃/SiN_xgate stacks is observed in comparison to control structures with SiN_xgate dielectrics directly indicating the negative capacitance contribution of the ferroelectric BaTiO₃layer. A significant reduction in the minimum subthreshold slope for the NC‐HEMTs is obtained in contrast to standard metal‐insulator‐semiconductor HEMTs with SiN_xgate dielectrics—97.1 mV dec⁻¹versus 145.6 mV dec⁻¹—with almost no hysteresis in theI_D–V_Gtransfer curves. These results are promising for the integration of ferroelectric perovskite oxides with III‐Nitride devices toward NC‐field‐effect transistor switches with reduced power consumption. 

   more » « less