Lihao Liu, Hui Bao, Mingda Zhang, Honghe Yao, Min Yang, Peng Huang, Kai Gu, Cheng Zhu, Yuanping Yi, Haizheng Zhong
Understanding the hole transport layers is fundamental to improve the stability of quantum-dot light-emitting diodes. This study investigates the short-term conductivity decay of freshly fabricated poly(9,9-dioctylfluorene-co-N-(4-(3-methylpropyl))diphenylamine) (TFB) films under applied voltage. In addition, the conductivity decay of freshly prepared TFB films can be partially recovered after short-term storage. The phenomenon is also observed in other hole transporting materials, such as PVK and PF8Cz. The decay dynamics can be described using the Kohlrausch–Williams–Watts stretched-exponential function. The temperature-dependent relaxation time extracted from the decay curves obeys an Arrhenius law, yielding an activation energy of 0.18 ± 0.03 eV. This value is in good agreement with the calculated reorganization energy associated with the hopping transport of charge carriers. Based on the results, conductivity decay of freshly fabricated TFB films during the initial short-term period can be explained by the coupling between electric field-induced polarization and carrier transport (denoted as polarization–conduction coupling).
了解空穴传输层是提高量子点发光二极管稳定性的基础。本文研究了新制备的聚(9,9-二辛基芴-co- n -（4-（3-甲基丙基））二苯胺（TFB）薄膜在外加电压作用下的短期电导率衰减。此外，新制备的TFB薄膜在短期储存后，电导率衰减可以部分恢复。在PVK和PF8Cz等其他空穴输运材料中也观察到这种现象。衰减动力学可以用Kohlrausch-Williams-Watts拉伸指数函数来描述。从衰变曲线中提取的温度随弛豫时间符合Arrhenius定律，得到的活化能为0.18±0.03 eV。该值与计算得到的载流子跳跃输运的重组能符合得很好。结果表明，新制备的TFB薄膜在初始短期内的电导率衰减可以解释为电场诱导极化和载流子输运之间的耦合（称为极化-传导耦合）。
{"title":"Conductivity decay in freshly fabricated TFB films","authors":"Lihao Liu, Hui Bao, Mingda Zhang, Honghe Yao, Min Yang, Peng Huang, Kai Gu, Cheng Zhu, Yuanping Yi, Haizheng Zhong","doi":"10.1063/5.0315386","DOIUrl":"https://doi.org/10.1063/5.0315386","url":null,"abstract":"Understanding the hole transport layers is fundamental to improve the stability of quantum-dot light-emitting diodes. This study investigates the short-term conductivity decay of freshly fabricated poly(9,9-dioctylfluorene-co-N-(4-(3-methylpropyl))diphenylamine) (TFB) films under applied voltage. In addition, the conductivity decay of freshly prepared TFB films can be partially recovered after short-term storage. The phenomenon is also observed in other hole transporting materials, such as PVK and PF8Cz. The decay dynamics can be described using the Kohlrausch–Williams–Watts stretched-exponential function. The temperature-dependent relaxation time extracted from the decay curves obeys an Arrhenius law, yielding an activation energy of 0.18 ± 0.03 eV. This value is in good agreement with the calculated reorganization energy associated with the hopping transport of charge carriers. Based on the results, conductivity decay of freshly fabricated TFB films during the initial short-term period can be explained by the coupling between electric field-induced polarization and carrier transport (denoted as polarization–conduction coupling).","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"11 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160128","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Han Gao, Jian-Huan Wang, Ji-Yin Wang, Jian-Jun Zhang, Hongqi Xu
We report an experimental study of induced superconductivity in Ge hut nanowire Josephson junctions. The Ge hut nanowires are grown on prepatterned SiGe ridges via molecular beam epitaxy and Josephson junction devices are fabricated by contacting the nanowires with Al electrodes. Low-temperature current-bias transport measurements of the Josephson junctions are performed and the measurements show that the devices exhibit gate-tunable supercurrent and excess current. The analysis of excess current indicates that the transparency of the Ge hut nanowire Josephson junctions is as high as 85%. Voltage-bias spectroscopy measurements of the devices show multiple Andreev reflections up to the fourth order. With magnetic field and temperature-dependent measurements of the multiple Andreev reflections, the critical field and the critical temperature of the induced superconductivity in the Josephson junctions are extracted to be ∼0.12 T and ∼1.4 K. The success in introducing superconductivity into Ge hut nanowires will stimulate their applications in building advanced quantum processors.
{"title":"Supercurrent and multiple Andreev reflections in Ge hut nanowire Josephson junctions","authors":"Han Gao, Jian-Huan Wang, Ji-Yin Wang, Jian-Jun Zhang, Hongqi Xu","doi":"10.1063/5.0302926","DOIUrl":"https://doi.org/10.1063/5.0302926","url":null,"abstract":"We report an experimental study of induced superconductivity in Ge hut nanowire Josephson junctions. The Ge hut nanowires are grown on prepatterned SiGe ridges via molecular beam epitaxy and Josephson junction devices are fabricated by contacting the nanowires with Al electrodes. Low-temperature current-bias transport measurements of the Josephson junctions are performed and the measurements show that the devices exhibit gate-tunable supercurrent and excess current. The analysis of excess current indicates that the transparency of the Ge hut nanowire Josephson junctions is as high as 85%. Voltage-bias spectroscopy measurements of the devices show multiple Andreev reflections up to the fourth order. With magnetic field and temperature-dependent measurements of the multiple Andreev reflections, the critical field and the critical temperature of the induced superconductivity in the Josephson junctions are extracted to be ∼0.12 T and ∼1.4 K. The success in introducing superconductivity into Ge hut nanowires will stimulate their applications in building advanced quantum processors.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"11 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Priyadharshini, V. Vijay, J. Archana, M. Navaneethan
Mg3Sb2-based Zintl compounds are promising p-type thermoelectric (TE) materials with a hexagonal crystal structure and are considered promising candidates due to their abundance in nature, low cost, and low toxicity. Here, the Sn-substituted p-type Mg3−xZnxSb2-based solid solution was synthesized via spark plasma sintering, and its transport properties were investigated through experimental and theoretical aspects. Sn at Sb sites in Mg1.8Zn1.2Sb2 softens the chemical bonding, and Sn-Sb 5p orbital overlapping introduces resonant states, resulting in an enhanced density of states. The improved carrier concentration of 1.47 × 1019 cm−3 and electrical conductivity of 324 S/cm, with the Seebeck coefficient of 133 μV/K, yielded a maximum power factor of 579.8 μW/mK2 at 753 K. Additionally, Sn doping induced lattice disorders, and point defects led to reduced the sound velocity of 2225 m/s, resulting in a low lattice thermal conductivity of 0.72 W/mK at 753 K. The synergistic effect of an enhanced power factor and suppressed thermal conductivity resulted in a maximum zT of 0.43 at 753 K for Mg1.8Zn1.2Sb1.94Sn0.06. This work underscored the critical role of resonant states and lattice disorders in boosting the TE performance of p-type Mg3−xZnxSb2.
{"title":"Tuning the phonon dynamics via Sn-resonant impurities assists strong anharmonicity in p -type Zintl Mg3Sb2","authors":"S. Priyadharshini, V. Vijay, J. Archana, M. Navaneethan","doi":"10.1063/5.0310517","DOIUrl":"https://doi.org/10.1063/5.0310517","url":null,"abstract":"Mg3Sb2-based Zintl compounds are promising p-type thermoelectric (TE) materials with a hexagonal crystal structure and are considered promising candidates due to their abundance in nature, low cost, and low toxicity. Here, the Sn-substituted p-type Mg3−xZnxSb2-based solid solution was synthesized via spark plasma sintering, and its transport properties were investigated through experimental and theoretical aspects. Sn at Sb sites in Mg1.8Zn1.2Sb2 softens the chemical bonding, and Sn-Sb 5p orbital overlapping introduces resonant states, resulting in an enhanced density of states. The improved carrier concentration of 1.47 × 1019 cm−3 and electrical conductivity of 324 S/cm, with the Seebeck coefficient of 133 μV/K, yielded a maximum power factor of 579.8 μW/mK2 at 753 K. Additionally, Sn doping induced lattice disorders, and point defects led to reduced the sound velocity of 2225 m/s, resulting in a low lattice thermal conductivity of 0.72 W/mK at 753 K. The synergistic effect of an enhanced power factor and suppressed thermal conductivity resulted in a maximum zT of 0.43 at 753 K for Mg1.8Zn1.2Sb1.94Sn0.06. This work underscored the critical role of resonant states and lattice disorders in boosting the TE performance of p-type Mg3−xZnxSb2.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"2021 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bismuth is recognized as one of the elemental solids with the strongest intrinsic spin–orbit coupling (SOC) and is widely used to induce topological characteristics in hetero-structures, particularly in chalcogenide-based material systems. Precise control over the crystalline quality and phase purity of bismuth is crucial for its characteristic topological features which can be achieved via molecular beam epitaxy (MBE). In this work, we investigate the electronic transport properties of MBE-grown Bi thin films deposited on Si(111) substrates. Robust spin–orbit coupling is manifested through pronounced weak anti-localization features observed under both out-of-plane and in-plane magnetic fields. In addition, a planar Hall response consistent with Rashba-type SOC emerges at room temperature, underscoring the strong interfacial and structural asymmetry in these MBE-grown Bi films. These films display a temperature-driven sign reversal in the Hall carrier concentration, indicating a transition in the dominant carrier type. Collectively, these observations advance the fundamental understanding of SOC-mediated transport in low-dimensional Bi and open avenues for engineering Rashba-dominated states in functional hetero-structures.
{"title":"Spin–orbit coupling signatures in polycrystalline bismuth thin films","authors":"Subhransu Kumar Negi, Rajib Sarkar, Sohini Guin, Naresh Shyaga, Dhavala Suri","doi":"10.1063/5.0315719","DOIUrl":"https://doi.org/10.1063/5.0315719","url":null,"abstract":"Bismuth is recognized as one of the elemental solids with the strongest intrinsic spin–orbit coupling (SOC) and is widely used to induce topological characteristics in hetero-structures, particularly in chalcogenide-based material systems. Precise control over the crystalline quality and phase purity of bismuth is crucial for its characteristic topological features which can be achieved via molecular beam epitaxy (MBE). In this work, we investigate the electronic transport properties of MBE-grown Bi thin films deposited on Si(111) substrates. Robust spin–orbit coupling is manifested through pronounced weak anti-localization features observed under both out-of-plane and in-plane magnetic fields. In addition, a planar Hall response consistent with Rashba-type SOC emerges at room temperature, underscoring the strong interfacial and structural asymmetry in these MBE-grown Bi films. These films display a temperature-driven sign reversal in the Hall carrier concentration, indicating a transition in the dominant carrier type. Collectively, these observations advance the fundamental understanding of SOC-mediated transport in low-dimensional Bi and open avenues for engineering Rashba-dominated states in functional hetero-structures.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"11 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yifan Zhang, Zhihao Zhao, Xinying Wang, Di Wang, Yu Li, Long Liu, Longchao Liu, Fengjun Dong, Biao Pan, Cheng Pan, Yan Sun, Guozhong Xing
The integration of artificial intelligence into space systems faces fundamental challenges in radiation resilience and energy-efficient computation. Here, we present a neuromorphic computing approach that proposes a strategy to transform these challenges into computational advantages via spintronic technology. We developed spin–orbit torque magnetic tunnel junction crossbar array harnesses radiation-induced fluctuations to enhance Hopfield neural network optimization, converting an environmental constraint into a functional benefit. When exposed to heavy ions (e.g., 209Bi23+), the system demonstrates remarkable radiation hardness with only 1.04% tunneling magnetoresistance degradation while maintaining operational stability. Implemented in a 4 Kb array, this neuro-inspired architecture solves the eight-city traveling salesman problem with 95.2% accuracy at 45.06 nJ energy consumption—outperforming conventional radiation-hardened approaches. Such a complementary experimental and simulation approach elaborates that the measured irradiation conductance fluctuations can be mapped to synaptic weights in a Hopfield network model, significantly enhancing its optimization capability. This work corroborates an emerging paradigm for adaptive, energy-efficient nanoscale artificial intelligence hardware that is designed to thrive in extreme environments, with implications for radiation-resilient neuromorphic architectures and edge computing.
{"title":"Harnessing radiation-induced fluctuations in spintronic neuromorphic hardware for energy-efficient aerospace computing","authors":"Yifan Zhang, Zhihao Zhao, Xinying Wang, Di Wang, Yu Li, Long Liu, Longchao Liu, Fengjun Dong, Biao Pan, Cheng Pan, Yan Sun, Guozhong Xing","doi":"10.1063/5.0303307","DOIUrl":"https://doi.org/10.1063/5.0303307","url":null,"abstract":"The integration of artificial intelligence into space systems faces fundamental challenges in radiation resilience and energy-efficient computation. Here, we present a neuromorphic computing approach that proposes a strategy to transform these challenges into computational advantages via spintronic technology. We developed spin–orbit torque magnetic tunnel junction crossbar array harnesses radiation-induced fluctuations to enhance Hopfield neural network optimization, converting an environmental constraint into a functional benefit. When exposed to heavy ions (e.g., 209Bi23+), the system demonstrates remarkable radiation hardness with only 1.04% tunneling magnetoresistance degradation while maintaining operational stability. Implemented in a 4 Kb array, this neuro-inspired architecture solves the eight-city traveling salesman problem with 95.2% accuracy at 45.06 nJ energy consumption—outperforming conventional radiation-hardened approaches. Such a complementary experimental and simulation approach elaborates that the measured irradiation conductance fluctuations can be mapped to synaptic weights in a Hopfield network model, significantly enhancing its optimization capability. This work corroborates an emerging paradigm for adaptive, energy-efficient nanoscale artificial intelligence hardware that is designed to thrive in extreme environments, with implications for radiation-resilient neuromorphic architectures and edge computing.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"30 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. C. Rodriguez E., H. Grisk, A. Anadón, H. Singh, G. Malinowski, M. Hehn, J. Curiale, J. Gorchon
Magnetic imaging techniques are widespread critical tools used in fields such as magnetism, spintronics, or even superconductivity. Among them, one of the most versatile methods is the magneto-optical Kerr effect. However, as soon as light is blocked from interacting with the magnetic layer, such as in deeply buried layers, optical techniques become ineffective. In this work, we present a spin accumulation based magneto-optical Kerr effect microscopy technique that enables imaging of a magnetic thin-film covered by thick and opaque metallic layers. The technique is based on the generation and detection of transient spin accumulations that propagate through the thick metallic layer. These spin accumulation signals are directly triggered and detected optically on the same side, lifting any substrate transparency requirements. The spin accumulation signals detected on a Cu layer decay with a characteristic length of 60 nm, much longer than the 12 nm optical penetration depth, allowing for the detection of magnetic contrast with Cu capping layers up to hundreds of nm. This method should enable magnetic imaging in a wide range of experiments where the surface of interest is covered by electrodes.
{"title":"Spin accumulation based deep MOKE microscopy","authors":"J. C. Rodriguez E., H. Grisk, A. Anadón, H. Singh, G. Malinowski, M. Hehn, J. Curiale, J. Gorchon","doi":"10.1063/5.0312055","DOIUrl":"https://doi.org/10.1063/5.0312055","url":null,"abstract":"Magnetic imaging techniques are widespread critical tools used in fields such as magnetism, spintronics, or even superconductivity. Among them, one of the most versatile methods is the magneto-optical Kerr effect. However, as soon as light is blocked from interacting with the magnetic layer, such as in deeply buried layers, optical techniques become ineffective. In this work, we present a spin accumulation based magneto-optical Kerr effect microscopy technique that enables imaging of a magnetic thin-film covered by thick and opaque metallic layers. The technique is based on the generation and detection of transient spin accumulations that propagate through the thick metallic layer. These spin accumulation signals are directly triggered and detected optically on the same side, lifting any substrate transparency requirements. The spin accumulation signals detected on a Cu layer decay with a characteristic length of 60 nm, much longer than the 12 nm optical penetration depth, allowing for the detection of magnetic contrast with Cu capping layers up to hundreds of nm. This method should enable magnetic imaging in a wide range of experiments where the surface of interest is covered by electrodes.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"35 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yuan Yu, Jiaqi Liu, Rujun Zhang, Qingying Luo, Si Zheng, Shengnan Yuan, Yufeng Zhou, Hairong Zheng, Feiyan Cai
High-throughput and biocompatible acoustofluidic manipulation of living cells and microparticles is essential for applications in cellular medicine, tissue engineering, and drug screening. Conventional surface acoustic wave (SAW)–based devices have been widely adopted; however, their high operating frequencies limit throughput, and the conversion of SAWs into leaky bulk waves in liquids induces strong acoustic streaming that compromises manipulation stability. Here, we present a low-frequency acoustofluidic device that exploits non-leaky quasi-Scholte waves in a piezoelectric thin plate to achieve high-throughput, stable, two-dimensional manipulation of particles and cells. Numerical simulations and laser Doppler vibrometry measurements confirm robust excitation of the quasi-Scholte mode, revealing evanescent acoustic fields with strong vertical gradients and well-defined in-plane standing waves in liquid. Experiments with microparticles and in vitro cells further demonstrate stable one- and two-dimensional patterning over large areas while maintaining high cell viability. This quasi-Scholte-wave-based acoustofluidic platform provides a reliable, effective, and high-throughput approach for precise manipulation of cells and biomaterials.
{"title":"High-throughput cell manipulation using low-frequency quasi-Scholte wave-based acoustofluidics","authors":"Yuan Yu, Jiaqi Liu, Rujun Zhang, Qingying Luo, Si Zheng, Shengnan Yuan, Yufeng Zhou, Hairong Zheng, Feiyan Cai","doi":"10.1063/5.0307916","DOIUrl":"https://doi.org/10.1063/5.0307916","url":null,"abstract":"High-throughput and biocompatible acoustofluidic manipulation of living cells and microparticles is essential for applications in cellular medicine, tissue engineering, and drug screening. Conventional surface acoustic wave (SAW)–based devices have been widely adopted; however, their high operating frequencies limit throughput, and the conversion of SAWs into leaky bulk waves in liquids induces strong acoustic streaming that compromises manipulation stability. Here, we present a low-frequency acoustofluidic device that exploits non-leaky quasi-Scholte waves in a piezoelectric thin plate to achieve high-throughput, stable, two-dimensional manipulation of particles and cells. Numerical simulations and laser Doppler vibrometry measurements confirm robust excitation of the quasi-Scholte mode, revealing evanescent acoustic fields with strong vertical gradients and well-defined in-plane standing waves in liquid. Experiments with microparticles and in vitro cells further demonstrate stable one- and two-dimensional patterning over large areas while maintaining high cell viability. This quasi-Scholte-wave-based acoustofluidic platform provides a reliable, effective, and high-throughput approach for precise manipulation of cells and biomaterials.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"70 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Regrown nonalloyed ohmic contacts for AlGaN/GaN high-electron-mobility transistors (HEMTs) were fabricated using low-temperature pulsed sputtering deposition (PSD) of highly Si-doped degenerate GaN (d-GaN) onto inductively coupled plasma-etched recesses. The regrown d-GaN (thickness: 250 nm) shows a sheet resistance of 7.2 Ω/sq. with a carrier concentration and mobility of 3.4×1020 cm−3 and 100 cm2 V−1 s−1, yielding a total contact resistance of 0.058±0.004 Ω mm. The inherent interface resistance between the PSD-regrown d-GaN and two-dimensional electron gas was estimated using the transfer length method to be 0.033±0.005 Ω mm, which is close to the single-interface quantum injection limit (0.026 Ω mm). The fabricated HEMT devices with 2 μm gate length exhibited good characteristics (maximum drain current density = 850 mA mm−1, maximum transconductance = 0.2 S mm−1, and on-resistance = 2.1 Ω mm). These results indicate that the low-temperature regrowth of nonalloyed d-GaN contacts with ultralow resistance using PSD is a scalable and low-thermal-budget route for future radio frequency transistors.
{"title":"Ultralow contact resistance of 0.058 Ω mm achieved by pulsed sputtering deposition of regrown degenerately doped GaN contacts for AlGaN/GaN high-electron-mobility transistors","authors":"Kohei Ueno, Kaito Fujisawa, Hiroshi Fujioka","doi":"10.1063/5.0311448","DOIUrl":"https://doi.org/10.1063/5.0311448","url":null,"abstract":"Regrown nonalloyed ohmic contacts for AlGaN/GaN high-electron-mobility transistors (HEMTs) were fabricated using low-temperature pulsed sputtering deposition (PSD) of highly Si-doped degenerate GaN (d-GaN) onto inductively coupled plasma-etched recesses. The regrown d-GaN (thickness: 250 nm) shows a sheet resistance of 7.2 Ω/sq. with a carrier concentration and mobility of 3.4×1020 cm−3 and 100 cm2 V−1 s−1, yielding a total contact resistance of 0.058±0.004 Ω mm. The inherent interface resistance between the PSD-regrown d-GaN and two-dimensional electron gas was estimated using the transfer length method to be 0.033±0.005 Ω mm, which is close to the single-interface quantum injection limit (0.026 Ω mm). The fabricated HEMT devices with 2 μm gate length exhibited good characteristics (maximum drain current density = 850 mA mm−1, maximum transconductance = 0.2 S mm−1, and on-resistance = 2.1 Ω mm). These results indicate that the low-temperature regrowth of nonalloyed d-GaN contacts with ultralow resistance using PSD is a scalable and low-thermal-budget route for future radio frequency transistors.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"36 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
High aspect ratio hole etching processes require high-speed etching of SiO2 and Si3N4 films. Cryogenic etching significantly increases the etch rates of these two films by lowering the substrate temperature. However, the etching behavior and mechanisms in the temperature range below −70 °C remain unclear. In this work, we investigate the etching behavior of blanket SiO2 films, from 25 to −200 °C, and examine the mechanisms through in situ analyses. Our results show that the etch rate at −100 °C is approximately 3.2 times higher than that at 25 °C, and is associated with the highest etching efficiency in our experiments. This enhancement in the etch rate is attributed to the co-adsorption of H2O and HF, which increases the number of etchants on the SiO2 surface. At temperatures lower than −100 °C, the solidification of H2O reduces the co-adsorption of HF, decreasing the etch rate. At temperatures below −150 °C, the etch rate declines further, owing to the reduced volatility of the reaction product SiF4. These findings provide valuable insights for optimizing etching processes under cryogenic conditions.
{"title":"In situ analysis of SiO2 films etched under cryogenic conditions using H2/F2/Ar gas mixture plasma","authors":"Yuma Kato, Junji Kataoka, Ryo Saito, Daiki Iino, Kazuaki Kurihara, Tetsuya Sato, Hiroyuki Fukumizu","doi":"10.1063/5.0303879","DOIUrl":"https://doi.org/10.1063/5.0303879","url":null,"abstract":"High aspect ratio hole etching processes require high-speed etching of SiO2 and Si3N4 films. Cryogenic etching significantly increases the etch rates of these two films by lowering the substrate temperature. However, the etching behavior and mechanisms in the temperature range below −70 °C remain unclear. In this work, we investigate the etching behavior of blanket SiO2 films, from 25 to −200 °C, and examine the mechanisms through in situ analyses. Our results show that the etch rate at −100 °C is approximately 3.2 times higher than that at 25 °C, and is associated with the highest etching efficiency in our experiments. This enhancement in the etch rate is attributed to the co-adsorption of H2O and HF, which increases the number of etchants on the SiO2 surface. At temperatures lower than −100 °C, the solidification of H2O reduces the co-adsorption of HF, decreasing the etch rate. At temperatures below −150 °C, the etch rate declines further, owing to the reduced volatility of the reaction product SiF4. These findings provide valuable insights for optimizing etching processes under cryogenic conditions.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"224 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ScAlN is a III-nitride ferroelectric material that has attracted considerable interest for its large remanent polarization, high thermal stability, and compatibility with GaN-based device platforms, and its properties strongly depend on growth conditions. In this study, ScAlN films were grown on Si-doped n-GaN/AlN/sapphire substrates by sputter epitaxy at growth temperatures of 420–675 °C, and their structural and ferroelectric characteristics were systematically investigated. X-ray diffraction and reciprocal space mapping revealed that the a-axis lattice constant increased, but the c-axis lattice constant simultaneously decreased, at growth temperatures above approximately 650 °C, indicating a temperature-induced modification of the ScAlN lattice. Positive-up–negative-down measurements showed a significant leakage current at temperatures above 550 °C, which prevented the saturation of the remanent polarization in the polarization–electric field characteristics. At lower growth temperatures, the films exhibited remanent polarization and coercive fields comparable to those reported for high-quality ScAlN films grown on GaN by molecular-beam epitaxy and metalorganic chemical vapor deposition. This result demonstrates that low-temperature sputter epitaxy can reproduce the intrinsic ferroelectric switching behavior of ScAlN. Thus, low-temperature sputter epitaxy effectively suppresses the leakage current and enables reliable ferroelectric switching, providing useful guidelines for optimizing ScAlN deposition processes for ferroelectric device applications.
{"title":"Structural and ferroelectric properties of sputter-epitaxial ScAlN on GaN grown at various temperatures","authors":"Sawaki Sato, Yusuke Wakamoto, Takuya Maeda, Hiroshi Funakubo, Kohei Ueno, Hiroshi Fujioka, Kazuhisa Ikeda, Atsushi Kobayashi","doi":"10.1063/5.0313954","DOIUrl":"https://doi.org/10.1063/5.0313954","url":null,"abstract":"ScAlN is a III-nitride ferroelectric material that has attracted considerable interest for its large remanent polarization, high thermal stability, and compatibility with GaN-based device platforms, and its properties strongly depend on growth conditions. In this study, ScAlN films were grown on Si-doped n-GaN/AlN/sapphire substrates by sputter epitaxy at growth temperatures of 420–675 °C, and their structural and ferroelectric characteristics were systematically investigated. X-ray diffraction and reciprocal space mapping revealed that the a-axis lattice constant increased, but the c-axis lattice constant simultaneously decreased, at growth temperatures above approximately 650 °C, indicating a temperature-induced modification of the ScAlN lattice. Positive-up–negative-down measurements showed a significant leakage current at temperatures above 550 °C, which prevented the saturation of the remanent polarization in the polarization–electric field characteristics. At lower growth temperatures, the films exhibited remanent polarization and coercive fields comparable to those reported for high-quality ScAlN films grown on GaN by molecular-beam epitaxy and metalorganic chemical vapor deposition. This result demonstrates that low-temperature sputter epitaxy can reproduce the intrinsic ferroelectric switching behavior of ScAlN. Thus, low-temperature sputter epitaxy effectively suppresses the leakage current and enables reliable ferroelectric switching, providing useful guidelines for optimizing ScAlN deposition processes for ferroelectric device applications.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"4 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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