Pub Date : 2024-10-28DOI: 10.1016/j.micrna.2024.208004
Yuchen Li , Min Zhou , Jinping Tian , Rongcao Yang
In this paper, a dual-function metamaterial device based on vanadium dioxide (VO2) and Dirac semimetal (DS) operating in terahertz (THz) frequency range is designed. The reversible phase transition properties of VO2 are exploited to achieve the dynamic switch between the function of broadband absorption and broadband polarization conversion. It is demonstrated that when VO2 is in the metallic state and the Fermi energy level () of DS is set to 30 the broadband absorption in the operating frequency range of 1.42–3.40 THz can be achieved, and its absorbance exceeds 90 % with a relative bandwidth of 82.16 %. When VO2 is in the insulating state and the of DS is set at 180 , the high efficient broadband polarization conversion can be obtained in the operating frequency range of 2.08–4.88 THz and the polarization conversion ratio (PCR) is greater than 90 % with a relative bandwidth of up to 80.46 %. Therefore, the proposed switchable dual-functional THz device can be extensively utilized in absorption, polarization conversion and other potential fields.
{"title":"A dynamically switchable and tunable metamaterial device based on vanadium dioxide and Dirac semimetal","authors":"Yuchen Li , Min Zhou , Jinping Tian , Rongcao Yang","doi":"10.1016/j.micrna.2024.208004","DOIUrl":"10.1016/j.micrna.2024.208004","url":null,"abstract":"<div><div>In this paper, a dual-function metamaterial device based on vanadium dioxide (VO<sub>2</sub>) and Dirac semimetal (DS) operating in terahertz (THz) frequency range is designed. The reversible phase transition properties of VO<sub>2</sub> are exploited to achieve the dynamic switch between the function of broadband absorption and broadband polarization conversion. It is demonstrated that when VO<sub>2</sub> is in the metallic state and the Fermi energy level (<span><math><mrow><msub><mi>E</mi><mi>f</mi></msub></mrow></math></span>) of DS is set to 30 <span><math><mrow><mtext>meV,</mtext></mrow></math></span> the broadband absorption in the operating frequency range of 1.42–3.40 THz can be achieved, and its absorbance exceeds 90 % with a relative bandwidth of 82.16 %. When VO<sub>2</sub> is in the insulating state and the <span><math><mrow><msub><mi>E</mi><mi>f</mi></msub></mrow></math></span> of DS is set at 180 <span><math><mrow><mtext>meV</mtext></mrow></math></span>, the high efficient broadband polarization conversion can be obtained in the operating frequency range of 2.08–4.88 THz and the polarization conversion ratio (PCR) is greater than 90 % with a relative bandwidth of up to 80.46 %. Therefore, the proposed switchable dual-functional THz device can be extensively utilized in absorption, polarization conversion and other potential fields.</div></div>","PeriodicalId":100923,"journal":{"name":"Micro and Nanostructures","volume":"196 ","pages":"Article 208004"},"PeriodicalIF":2.7,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-24DOI: 10.1016/j.micrna.2024.207995
Anupama , Sonam Rewari , Neeta Pandey
In this paper, Core Shell Dual Metal Gate Stack Junctionless Accumulation Mode Nanowire FET (CS-DM-GS-JAMNWFET) is proposed, which has enhanced performance and is suitable for analog and digital applications. A high-k gate stack engineering, Hafnium Oxide (HfO2) is deployed in the outer as well as inner gate oxides of the core shell structure. The proposed device is compared with CS-DM-JAMNWFET, CS-SM-JAMNWFET, DM-GS-JAMNWFET, DM-JAMNWFET, and SM-JAMNWFET by maintaining a constant threshold voltage for all structures. The proposed CS-DM-GS-JAMNWFET provides a substantial reduction in subthreshold current with a high Ion/Ioff ratio as compared to other competent device structures. Also, the proposed device exhibits improvements in various parameters compared to the SM-JAMNWFET. It shows improvement in drain current (2.27 times), output conductance (2.14 times), subthreshold swing (0.94 times), transconductance (2.47 times), gate capacitance (2.00 times), cut-off frequency (1.24 times), intrinsic gain (12.95 times), current gain (1.46), Ion/Ioff ratio (6.15 times), unilateral power gain (1.09 times), maximum transducer power gain (1.08 times), Transconductance Generation factor (1.08 times), gain frequency product (14.61 times), transconductance frequency product (1.32 times), and gain transconductance frequency product (17.27 times). These benefits are due to combined advantages of the dual metal high-k dielectric HfO2 structure in core shell JAM FET, which enhances the device's gate dominance over the channel with high driving current.
{"title":"Numerical simulation of core shell dual metal gate stack junctionless accumulation mode nanowire FET (CS-DM-GS-JAMNWFET) for low power digital applications","authors":"Anupama , Sonam Rewari , Neeta Pandey","doi":"10.1016/j.micrna.2024.207995","DOIUrl":"10.1016/j.micrna.2024.207995","url":null,"abstract":"<div><div>In this paper, Core Shell Dual Metal Gate Stack Junctionless Accumulation Mode Nanowire FET (CS-DM-GS-JAMNWFET) is proposed, which has enhanced performance and is suitable for analog and digital applications. A high-k gate stack engineering, Hafnium Oxide (HfO<sub>2</sub>) is deployed in the outer as well as inner gate oxides of the core shell structure. The proposed device is compared with CS-DM-JAMNWFET, CS-SM-JAMNWFET, DM-GS-JAMNWFET, DM-JAMNWFET, and SM-JAMNWFET by maintaining a constant threshold voltage for all structures. The proposed CS-DM-GS-JAMNWFET provides a substantial reduction in subthreshold current with a high I<sub>on</sub>/I<sub>off</sub> ratio as compared to other competent device structures. Also, the proposed device exhibits improvements in various parameters compared to the SM-JAMNWFET. It shows improvement in drain current (2.27 times), output conductance (2.14 times), subthreshold swing (0.94 times), transconductance (2.47 times), gate capacitance (2.00 times), cut-off frequency (1.24 times), intrinsic gain (12.95 times), current gain (1.46), I<sub>on</sub>/I<sub>off</sub> ratio (6.15 times), unilateral power gain (1.09 times), maximum transducer power gain (1.08 times), Transconductance Generation factor (1.08 times), gain frequency product (14.61 times), transconductance frequency product (1.32 times), and gain transconductance frequency product (17.27 times). These benefits are due to combined advantages of the dual metal high-k dielectric HfO<sub>2</sub> structure in core shell JAM FET, which enhances the device's gate dominance over the channel with high driving current.</div></div>","PeriodicalId":100923,"journal":{"name":"Micro and Nanostructures","volume":"196 ","pages":"Article 207995"},"PeriodicalIF":2.7,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142699420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-23DOI: 10.1016/j.micrna.2024.208001
Xingyu Wei, Hujun Jia, Linna Zhao, Qiyu Su, Weitao Cao, Wanli Yang, Zhen Cao, Yintang Yang
This paper presents a biosensor based on a finger-inserted inverted T-shaped vertical tunneling field effect transistor (FP-T-TFET). In order to improve the sensitivity and performance of the biosensor, a finger-inserted contact between the source and the channel is used. A comparative analysis between the biosensor based on FP-T-TFET and conventional inverted T-shaped TFET (T-TFET) is simulated for the electrical properties and sensitivity of neutral biomolecules with different dielectric constants and charged biomolecules with different charge densities. The noise analysis of the proposed structure is also performed. Then, the effects of insertion finger distribution, cavity size and filling volume on the performance of FP-T-TFET are investigated. Finally, the structure was subjected to linear analysis, in which the pearson coefficient was 0.92, indicating that the structure has good linear correlation. The results show that the FP-T-TFET biosensor has higher sensitivity in detecting various neutral and charged biomolecules. All device simulations were performed in the TCAD environment with a well-calibrated structure.
本文介绍了一种基于手指插入式倒 T 型垂直隧道场效应晶体管（FP-T-TFET）的生物传感器。为了提高生物传感器的灵敏度和性能，在源极和沟道之间使用了手指插入式触点。针对不同介电常数的中性生物分子和不同电荷密度的带电生物分子的电学特性和灵敏度，模拟了基于 FP-T-TFET 的生物传感器与传统的倒 T 型 TFET（T-TFET）之间的比较分析。此外，还对拟议结构进行了噪声分析。然后，研究了插入指分布、空腔尺寸和填充体积对 FP-T-TFET 性能的影响。最后，对该结构进行了线性分析，皮尔逊系数为 0.92，表明该结构具有良好的线性相关性。结果表明，FP-T-TFET 生物传感器在检测各种中性和带电生物分子时具有更高的灵敏度。所有器件仿真都是在 TCAD 环境下进行的，结构校准良好。
{"title":"Sensitivity analysis of an inverted T-shaped vertical tunneling field effect transistor biosensor based on inserted finger type","authors":"Xingyu Wei, Hujun Jia, Linna Zhao, Qiyu Su, Weitao Cao, Wanli Yang, Zhen Cao, Yintang Yang","doi":"10.1016/j.micrna.2024.208001","DOIUrl":"10.1016/j.micrna.2024.208001","url":null,"abstract":"<div><div>This paper presents a biosensor based on a finger-inserted inverted T-shaped vertical tunneling field effect transistor (FP-T-TFET). In order to improve the sensitivity and performance of the biosensor, a finger-inserted contact between the source and the channel is used. A comparative analysis between the biosensor based on FP-T-TFET and conventional inverted T-shaped TFET (T-TFET) is simulated for the electrical properties and sensitivity of neutral biomolecules with different dielectric constants and charged biomolecules with different charge densities. The noise analysis of the proposed structure is also performed. Then, the effects of insertion finger distribution, cavity size and filling volume on the performance of FP-T-TFET are investigated. Finally, the structure was subjected to linear analysis, in which the pearson coefficient was 0.92, indicating that the structure has good linear correlation. The results show that the FP-T-TFET biosensor has higher sensitivity in detecting various neutral and charged biomolecules. All device simulations were performed in the TCAD environment with a well-calibrated structure.</div></div>","PeriodicalId":100923,"journal":{"name":"Micro and Nanostructures","volume":"196 ","pages":"Article 208001"},"PeriodicalIF":2.7,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528599","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-23DOI: 10.1016/j.micrna.2024.208000
Jinji Si , Qingyu Hou , Weiya Li , Yi Liu , Riguleng Si
The preparation of single-layer GaN by chemical vapor deposition inevitably generates H interstitials. In this study, the optical properties of single-layer Ga36N36, Ga34LiN36 and Ga34HiLiN36 (0 0 1) surfaces were investigated by using the first-principles method. In the presence of Li doping and H interstitial, the dielectric function and reflectivity red-shifted in the low-energy range and the dielectric function and reflectivity of the Ga36N36 improved. In the visible range of the absorption spectrum, the impurity-containing surfaces red-shifted, and the light absorption on the Ga36N36 improved. The Ga34HiLiN36 (0 0 1) surface performed better as a photovoltaic material than other surfaces.
通过化学气相沉积法制备单层氮化镓不可避免地会产生 H 间隙。本研究采用第一原理方法研究了单层 Ga36N36、Ga34LiN36 和 Ga34HiLiN36 (0 0 1) 表面的光学特性。在掺入 Li 和 H 间质的情况下，Ga36N36 的介电常数和反射率在低能量范围内发生了红移，介电常数和反射率得到了改善。在吸收光谱的可见光范围内，含杂质的表面发生了红移，Ga36N36 的光吸收得到了改善。Ga34HiLiN36 (0 0 1) 表面作为光电材料的性能优于其他表面。
{"title":"First principles study of point defects and Li doping on the electronic structure and photovoltaic performance of single-layer GaN","authors":"Jinji Si , Qingyu Hou , Weiya Li , Yi Liu , Riguleng Si","doi":"10.1016/j.micrna.2024.208000","DOIUrl":"10.1016/j.micrna.2024.208000","url":null,"abstract":"<div><div>The preparation of single-layer GaN by chemical vapor deposition inevitably generates H interstitials. In this study, the optical properties of single-layer Ga<sub>36</sub>N<sub>36</sub>, Ga<sub>34</sub>LiN<sub>36</sub> and Ga<sub>34</sub>H<sub>i</sub>LiN<sub>36</sub> (0 0 1) surfaces were investigated by using the first-principles method. In the presence of Li doping and H interstitial, the dielectric function and reflectivity red-shifted in the low-energy range and the dielectric function and reflectivity of the Ga<sub>36</sub>N<sub>36</sub> improved. In the visible range of the absorption spectrum, the impurity-containing surfaces red-shifted, and the light absorption on the Ga<sub>36</sub>N<sub>36</sub> improved. The Ga<sub>34</sub>H<sub>i</sub>LiN<sub>36</sub> (0 0 1) surface performed better as a photovoltaic material than other surfaces.</div></div>","PeriodicalId":100923,"journal":{"name":"Micro and Nanostructures","volume":"196 ","pages":"Article 208000"},"PeriodicalIF":2.7,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528601","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gas sensing requires highly sensitive and selective sensor technologies for environmental monitoring, industrial safety, and public health objectives. Although conventional MOSFET-based gas sensors are widely utilized, their detection of low quantities of gases, such as ammonia, is hindered by a number of severe constraints. TFET is emerged as the better device than MOSFET, particularly for the sensing applications. In this work we discussed the source engineered and shape engineered techniques to improve the performance of TFETs, specifically for ammonia gas detection. Comprehensive simulations on SILVACO TCAD and compared the four TFET structures SiGe-pocket DGTFET, SiGe-pocket vertical TFET SiGe-pocket Z-shape TFET, and SiGe-pocket U-shape TFET structure on the basis of various electrical characterization parameters. Significant improvements in efficiency and sensitivity are obtained by adjusting the work function of the molybdenum (4.40–4.60 eV) catalytic gate metal to find the optimal values. The findings reveal that the SiGe-pocket U-shape TFET structure exhibits superior performance, demonstrating an ION of 8.01 × 10−4 A/μm, an ION/IOFF ratio of 1.25×1013, and an OFF current sensitivity (SOFF) of 1.262. These results highlight the enhanced sensitivity and efficacy of the proposed SiGe-pocket U-shape tunnel FET in ammonia gas sensing applications, making it a promising candidate for practical uses in environmental monitoring and industrial safety.
气体传感需要高灵敏度和高选择性的传感器技术，以实现环境监测、工业安全和公共卫生目标。虽然基于 MOSFET 的传统气体传感器得到了广泛应用，但它们对氨等低量气体的检测受到了许多严重限制。与 MOSFET 相比，TFET 是一种更好的器件，尤其适用于传感应用。在这项工作中，我们讨论了改善 TFET 性能的源工程和形状工程技术，特别是在氨气检测方面。我们在 SILVACO TCAD 上进行了全面模拟，并根据各种电气特性参数比较了四种 TFET 结构：SiGe-pocket DGTFET、SiGe-pocket 垂直 TFET、SiGe-pocket Z 形 TFET 和 SiGe-pocket U 形 TFET 结构。通过调整钼（4.40-4.60 eV）催化栅金属的功函数，找到最佳值，从而显著提高了效率和灵敏度。研究结果表明，SiGe-pocket U 形 TFET 结构具有卓越的性能，其离子强度为 8.01 × 10-4 A/μm，离子强度/离子强度比为 1.25×1013，关断电流灵敏度（SOFF）为 1.262。这些结果凸显了所提出的 SiGe-pocket U 形隧道场效应晶体管在氨气传感应用中的灵敏度和功效，使其有望在环境监测和工业安全领域得到实际应用。
{"title":"Impact of SiGe pocket on different shape TFET structures for gas sensing application","authors":"Yeroosan Getachew Hirphaa, Avtar Singh, Tadesse Hailu, Chaliti Fikadu Wakweya","doi":"10.1016/j.micrna.2024.207998","DOIUrl":"10.1016/j.micrna.2024.207998","url":null,"abstract":"<div><div>Gas sensing requires highly sensitive and selective sensor technologies for environmental monitoring, industrial safety, and public health objectives. Although conventional MOSFET-based gas sensors are widely utilized, their detection of low quantities of gases, such as ammonia, is hindered by a number of severe constraints. TFET is emerged as the better device than MOSFET, particularly for the sensing applications. In this work we discussed the source engineered and shape engineered techniques to improve the performance of TFETs, specifically for ammonia gas detection. Comprehensive simulations on SILVACO TCAD and compared the four TFET structures SiGe-pocket DGTFET, SiGe-pocket vertical TFET SiGe-pocket Z-shape TFET, and SiGe-pocket U-shape TFET structure on the basis of various electrical characterization parameters. Significant improvements in efficiency and sensitivity are obtained by adjusting the work function of the molybdenum (4.40–4.60 eV) catalytic gate metal to find the optimal values. The findings reveal that the SiGe-pocket U-shape TFET structure exhibits superior performance, demonstrating an I<sub>ON</sub> of 8.01 × 10<sup>−4</sup> A/μm, an I<sub>ON</sub>/I<sub>OFF</sub> ratio of 1.25×10<sup>13</sup>, and an OFF current sensitivity (S<sub>OFF</sub>) of 1.262. These results highlight the enhanced sensitivity and efficacy of the proposed SiGe-pocket U-shape tunnel FET in ammonia gas sensing applications, making it a promising candidate for practical uses in environmental monitoring and industrial safety.</div></div>","PeriodicalId":100923,"journal":{"name":"Micro and Nanostructures","volume":"196 ","pages":"Article 207998"},"PeriodicalIF":2.7,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528600","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-21DOI: 10.1016/j.micrna.2024.207999
Yongbo Li , Xinping Guo , Wenbo Xiao , Huaming Wu , Bin Liu
The property changes between APbBr3 (A = Li, Na) and LiPbBr3/NaPbBr3 superlattice (LiNaPb2Br6), as well as the electronic structure and optical properties of LiNaPb2Br6 under various pressures, have been investigated using the GGA-PBE method based on first-principles. The research shows that the band gap (Eg) value of LiNaPb2Br6 is 1.674 eV at 0 GPa, which is between that of LiPbBr3 and NaPbBr3. Meanwhile, the results indicate that the Eg of LiNaPb2Br6 gradually decreases with the increase in pressure, reaching 0.080 eV at 7 GPa, and its valence band top crosses the Fermi level at 8 GPa. Therefore, by combining the construction of superlattices with the application of pressure, the Eg of LiNaPb2Br6 can be continuously regulated in the range of 0–1.674 eV. Since the optical properties of a material primarily depend on its band structure, the optical properties of LiNaPb2Br6 can be widely adjusted by continuously tuning the Eg of this superlattice. The calculated results demonstrate that the optical properties of LiNaPb2Br6 were optimized in comparison to APbBr3 (A = Li, Na). In addition, the increase in pressure improves the absorption capability of LiNaPb2Br6 in both the visible and ultraviolet regions, thereby expanding the potential applications of LiNaPb2Br6 in the optical field.
{"title":"Study on the tunable band gap of LiNaPb2Br6 superlattice and its optical properties","authors":"Yongbo Li , Xinping Guo , Wenbo Xiao , Huaming Wu , Bin Liu","doi":"10.1016/j.micrna.2024.207999","DOIUrl":"10.1016/j.micrna.2024.207999","url":null,"abstract":"<div><div>The property changes between APbBr<sub>3</sub> (A = Li, Na) and LiPbBr<sub>3</sub>/NaPbBr<sub>3</sub> superlattice (LiNaPb<sub>2</sub>Br<sub>6</sub>), as well as the electronic structure and optical properties of LiNaPb<sub>2</sub>Br<sub>6</sub> under various pressures, have been investigated using the GGA-PBE method based on first-principles. The research shows that the band gap (E<sub>g</sub>) value of LiNaPb<sub>2</sub>Br<sub>6</sub> is 1.674 eV at 0 GPa, which is between that of LiPbBr<sub>3</sub> and NaPbBr<sub>3</sub>. Meanwhile, the results indicate that the E<sub>g</sub> of LiNaPb<sub>2</sub>Br<sub>6</sub> gradually decreases with the increase in pressure, reaching 0.080 eV at 7 GPa, and its valence band top crosses the Fermi level at 8 GPa. Therefore, by combining the construction of superlattices with the application of pressure, the E<sub>g</sub> of LiNaPb<sub>2</sub>Br<sub>6</sub> can be continuously regulated in the range of 0–1.674 eV. Since the optical properties of a material primarily depend on its band structure, the optical properties of LiNaPb<sub>2</sub>Br<sub>6</sub> can be widely adjusted by continuously tuning the E<sub>g</sub> of this superlattice. The calculated results demonstrate that the optical properties of LiNaPb<sub>2</sub>Br<sub>6</sub> were optimized in comparison to APbBr<sub>3</sub> (A = Li, Na). In addition, the increase in pressure improves the absorption capability of LiNaPb<sub>2</sub>Br<sub>6</sub> in both the visible and ultraviolet regions, thereby expanding the potential applications of LiNaPb<sub>2</sub>Br<sub>6</sub> in the optical field.</div></div>","PeriodicalId":100923,"journal":{"name":"Micro and Nanostructures","volume":"196 ","pages":"Article 207999"},"PeriodicalIF":2.7,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-18DOI: 10.1016/j.micrna.2024.207996
Yuhui Chen , Yanheng Song , Zhiwei Wang , Jiayue Li , Junchen Zhou , Yufei Hou , Mei Zhou
This paper proposes four new gradient composition electron blocking layer (EBL) structures to enhance the photoelectric performance of GaN-based green laser diodes (LDs). The optical and electrical properties of new structure LDs are theoretically analyzed by LASTIP. It is observed that the implementation of a gradient composition EBL structure increases the effective barrier height for electrons, thereby better inhibiting the electron current overflow from the active region. In addition, the optical field leakage is effectively suppressed, lower threshold current and higher output power are obtained. The four different new structures have obvious differences in the improvement of the hole current injection and slope efficiency of multiple quantum well (MQW) LDs, and the underlying reasons for these phenomena are explored. Simulation results indicate that adopting a gradually descending Al component EBL structure yields optimal improvements in the photoelectric performance of LDs.
{"title":"Improving photoelectric characteristics of GaN-based green laser diodes by inserting electron blocking layer with gradient Al composition","authors":"Yuhui Chen , Yanheng Song , Zhiwei Wang , Jiayue Li , Junchen Zhou , Yufei Hou , Mei Zhou","doi":"10.1016/j.micrna.2024.207996","DOIUrl":"10.1016/j.micrna.2024.207996","url":null,"abstract":"<div><div>This paper proposes four new gradient composition electron blocking layer (EBL) structures to enhance the photoelectric performance of GaN-based green laser diodes (LDs). The optical and electrical properties of new structure LDs are theoretically analyzed by LASTIP. It is observed that the implementation of a gradient composition EBL structure increases the effective barrier height for electrons, thereby better inhibiting the electron current overflow from the active region. In addition, the optical field leakage is effectively suppressed, lower threshold current and higher output power are obtained. The four different new structures have obvious differences in the improvement of the hole current injection and slope efficiency of multiple quantum well (MQW) LDs, and the underlying reasons for these phenomena are explored. Simulation results indicate that adopting a gradually descending Al component EBL structure yields optimal improvements in the photoelectric performance of LDs.</div></div>","PeriodicalId":100923,"journal":{"name":"Micro and Nanostructures","volume":"196 ","pages":"Article 207996"},"PeriodicalIF":2.7,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529047","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-12DOI: 10.1016/j.micrna.2024.207994
Zohreh Roustaei, Ali A. Orouji
The ability to control the gate capacitances is crucial for high-frequency applications, as it affects the device's frequency characteristics, gain and power handling capabilities. We present a 4H–SiC metal-semiconductor field-effect transistor (MESFET) with high gate capacitance control ability for high-frequency applications. The proposed structure (GCC-MESFET) consists of a step gate and a SiC well for adjusting the channel depletion layer and modifying the channel charges. Therefore, the gate capacitances will be controlled (GCC-MESFET). The proposed structure significantly improves the cut-off frequency (fT) and maximum oscillation frequency (fmax). The fT has increased from 23.5 GHz to 33 GHz and the fmax from 50.1 GHz to 54.4 GHz in the proposed structure compared to a conventional structure (C-MESFET). The results show that the DC maximum output power density (Pmax), DC transconductance (gm), cut-off frequency (fT) and maximum oscillation frequency (fmax) of GCC-MESFET improve in comparison with a conventional structure (C-MESFET). It is necessary to mention that the drain current and the breakdown voltage of the proposed structure increase by 48 % and 20 % respectively, compared with the C-MESFET structure due to modifying the channel charges and adjusting the electric field. So, the proposed structure can be used for high current, high voltage, high-power and high frequency applications.
{"title":"Novel 4H–SiC MESFET with high ability in gate capacitances control for high frequency applications","authors":"Zohreh Roustaei, Ali A. Orouji","doi":"10.1016/j.micrna.2024.207994","DOIUrl":"10.1016/j.micrna.2024.207994","url":null,"abstract":"<div><div>The ability to control the gate capacitances is crucial for high-frequency applications, as it affects the device's frequency characteristics, gain and power handling capabilities. We present a 4H–SiC metal-semiconductor field-effect transistor (MESFET) with high gate capacitance control ability for high-frequency applications. The proposed structure (GCC-MESFET) consists of a step gate and a SiC well for adjusting the channel depletion layer and modifying the channel charges. Therefore, the gate capacitances will be controlled (GCC-MESFET). The proposed structure significantly improves the cut-off frequency (f<sub>T</sub>) and maximum oscillation frequency (f<sub>max</sub>). The f<sub>T</sub> has increased from 23.5 GHz to 33 GHz and the f<sub>max</sub> from 50.1 GHz to 54.4 GHz in the proposed structure compared to a conventional structure (C-MESFET). The results show that the DC maximum output power density (P<sub>max</sub>), DC <em>trans</em>conductance (g<sub>m</sub>), cut-off frequency (f<sub>T</sub>) and maximum oscillation frequency (f<sub>max</sub>) of GCC-MESFET improve in comparison with a conventional structure (C-MESFET). It is necessary to mention that the drain current and the breakdown voltage of the proposed structure increase by 48 % and 20 % respectively, compared with the C-MESFET structure due to modifying the channel charges and adjusting the electric field. So, the proposed structure can be used for high current, high voltage, high-power and high frequency applications.</div></div>","PeriodicalId":100923,"journal":{"name":"Micro and Nanostructures","volume":"196 ","pages":"Article 207994"},"PeriodicalIF":2.7,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142444834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recently, lead-based perovskite solar cells (PSCs) have gained significant attention in the photovoltaic industry due to their remarkable properties such as high bandgap and high absorption coefficient. However, challenges such as toxicity, instability, and short shelf life limit the use of inorganic-organic lead-based PSCs. To address these issues, researchers introduced eco-friendly, lead-free, and stable cesium titanium (Cs2TiBr6) single-halide absorber material. The aim of this work is to perform the numerical modelling and simulation of FTO/SnO2/Cs2TiBr6/CBTS/Au structure incorporating interfacial defect layers (IDL) using SCAPS-1D to examine and study its characteristics properties about various photovoltaic (PV) parameters such as light-absorbing layer thickness, charge transport layer thickness, doping, defect density, operating temperature, and quantum efficiency (QE). After evaluating these parameters, the proposed single-halide Cs2TiBr6-based structure shows superior performance as compared to previously reported experimental and simulation-based Cs2TiBr6 perovskite structures. The results show a maximum power conversion efficiency (PCE) of 24.24 %, with a fill factor (FF) of 88.9 %, an open-circuit voltage (VOC) of 1.31 V, and a short-circuit current density (JSC) of 20.76 mA/cm2. This work encourages researchers to develop low-toxic, and stable PSCs for the future solar cell industry.
{"title":"Lead-free Cs2TiBr6 perovskite solar cells achieving high power conversion efficiency through device simulation","authors":"Syamantak Gupta , Jaspinder Kaur , Rikmantra Basu , Ajay Kumar Sharma , Rahul Pandey , Jaya Madan","doi":"10.1016/j.micrna.2024.207991","DOIUrl":"10.1016/j.micrna.2024.207991","url":null,"abstract":"<div><div>Recently, lead-based perovskite solar cells (PSCs) have gained significant attention in the photovoltaic industry due to their remarkable properties such as high bandgap and high absorption coefficient. However, challenges such as toxicity, instability, and short shelf life limit the use of inorganic-organic lead-based PSCs. To address these issues, researchers introduced eco-friendly, lead-free, and stable cesium titanium (Cs<sub>2</sub>TiBr<sub>6</sub>) single-halide absorber material. The aim of this work is to perform the numerical modelling and simulation of FTO/SnO<sub>2</sub>/Cs<sub>2</sub>TiBr<sub>6</sub>/CBTS/Au structure incorporating interfacial defect layers (IDL) using SCAPS-1D to examine and study its characteristics properties about various photovoltaic (PV) parameters such as light-absorbing layer thickness, charge transport layer thickness, doping, defect density, operating temperature, and quantum efficiency (QE). After evaluating these parameters, the proposed single-halide Cs<sub>2</sub>TiBr<sub>6</sub>-based structure shows superior performance as compared to previously reported experimental and simulation-based Cs<sub>2</sub>TiBr<sub>6</sub> perovskite structures. The results show a maximum power conversion efficiency (PCE) of 24.24 %, with a fill factor (FF) of 88.9 %, an open-circuit voltage (V<sub>OC</sub>) of 1.31 V, and a short-circuit current density (J<sub>SC</sub>) of 20.76 mA/cm<sup>2</sup>. This work encourages researchers to develop low-toxic, and stable PSCs for the future solar cell industry.</div></div>","PeriodicalId":100923,"journal":{"name":"Micro and Nanostructures","volume":"196 ","pages":"Article 207991"},"PeriodicalIF":2.7,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428816","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-05DOI: 10.1016/j.micrna.2024.207993
Xiao Xu , Jian Zhao , Wei Gao , Zhen-Hua Li , Ting-Ting Shi , Peng-Ze Song , Man-Chao He
The interaction between water and soft rock rich in clay minerals is one of the main factors causing damage in soft rock tunnel engineering. The effects of temperature on the atomic structure and water absorption capacities of clay minerals cannot be ignored. In the present study, the influence of temperature on the microstructure of Mg-montmorillonite and the thermal stability of the Mg-montmorillonite (010) surface were calculated based on density functional theory. Furthermore, the adsorption properties of H2O molecules within different coverages (0 < Θ ≤ 1.0 ML) on the (010) surface were investigated in the temperature range of 0–900 K. First, the volume of Mg-montmorillonite expanded significantly with increasing temperature along the z-axis direction. The surface energy of the Mg-montmorillonite (010) surface decreased with increasing temperature, indicating that the high temperature weakened the interatomic interactions on the surface. Moreover, the calculations demonstrated that H2O molecules could still be stably adsorbed on the Mg-montmorillonite (010) surface at different temperatures, and the order of stable adsorption configurations for a single H2O molecule was hollow > bridge > interlayer bridge > top sites. With increasing coverage of H2O molecules, the adsorption energies increased for the top sites, while decreased for the bridge, hollow, and interlayer bridge sites at high temperature. In addition, the changes in atomic structure and electronic characteristics during water absorption were further explored by calculating the ICOHP, PDOS, and lattice relaxation.
水与富含粘土矿物的软岩之间的相互作用是造成软岩隧道工程破坏的主要因素之一。温度对粘土矿物原子结构和吸水能力的影响不容忽视。本研究基于密度泛函理论计算了温度对镁蒙脱石微观结构的影响以及镁蒙脱石（010）表面的热稳定性。首先，随着温度的升高，镁蒙脱石的体积沿 Z 轴方向显著增大。镁蒙脱石（010）表面的表面能随着温度的升高而降低，这表明高温削弱了表面原子间的相互作用。此外，计算表明，H2O 分子在不同温度下仍能稳定地吸附在镁蒙脱石（010）表面，单个 H2O 分子的稳定吸附构型顺序为空心位、桥位、层间桥位、顶位。随着 H2O 分子覆盖率的增加，高温下顶部位点的吸附能增加，而桥接位点、空心位点和层间桥接位点的吸附能降低。此外，通过计算 ICOHP、PDOS 和晶格弛豫，进一步探讨了吸水过程中原子结构和电子特性的变化。
{"title":"A first-principles study of the effects of temperature on the atomic and electronic structures of Mg-montmorillonite with H2O molecule adsorption","authors":"Xiao Xu , Jian Zhao , Wei Gao , Zhen-Hua Li , Ting-Ting Shi , Peng-Ze Song , Man-Chao He","doi":"10.1016/j.micrna.2024.207993","DOIUrl":"10.1016/j.micrna.2024.207993","url":null,"abstract":"<div><div>The interaction between water and soft rock rich in clay minerals is one of the main factors causing damage in soft rock tunnel engineering. The effects of temperature on the atomic structure and water absorption capacities of clay minerals cannot be ignored. In the present study, the influence of temperature on the microstructure of Mg-montmorillonite and the thermal stability of the Mg-montmorillonite (010) surface were calculated based on density functional theory. Furthermore, the adsorption properties of H<sub>2</sub>O molecules within different coverages (0 < Θ ≤ 1.0 ML) on the (010) surface were investigated in the temperature range of 0–900 K. First, the volume of Mg-montmorillonite expanded significantly with increasing temperature along the <em>z</em>-axis direction. The surface energy of the Mg-montmorillonite (010) surface decreased with increasing temperature, indicating that the high temperature weakened the interatomic interactions on the surface. Moreover, the calculations demonstrated that H<sub>2</sub>O molecules could still be stably adsorbed on the Mg-montmorillonite (010) surface at different temperatures, and the order of stable adsorption configurations for a single H<sub>2</sub>O molecule was hollow > bridge > interlayer bridge > top sites. With increasing coverage of H<sub>2</sub>O molecules, the adsorption energies increased for the top sites, while decreased for the bridge, hollow, and interlayer bridge sites at high temperature. In addition, the changes in atomic structure and electronic characteristics during water absorption were further explored by calculating the ICOHP, PDOS, and lattice relaxation.</div></div>","PeriodicalId":100923,"journal":{"name":"Micro and Nanostructures","volume":"196 ","pages":"Article 207993"},"PeriodicalIF":2.7,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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