Pub Date : 2024-03-11DOI: 10.1088/1361-6641/ad3275
C. Deng, Zhizhong Chen, Yifan Chen, Qian Sun, J. Nie, Z. Pan, Haodong Zhang, Boyan Dong, Yian Chen, Daqi Wang, Yuchen Li, Weihua Chen, Xiangning Kang, Qi Wang, Guoyi Zhang, B. Shen, Huijuan Wang, Fei Wang, Wei Wang, Zhongxiao Li
Quantum dots (QDs) have been paid much attention on the color conversion for light-emitting diode (LED) in micro-display recently. However, it is hard to achieve high color conversion efficiency in a thin QD layer. In this paper, we fabricated silver nanoparticles (Ag NPs) with radii ranging mostly from 25 to 35 nm on a blue LED with a peak wavelength of 450 nm, then spin-coated QDs with a peak wavelength of 565 nm. Scanning electron microscopy (SEM), cathodoluminescence (CL), photoluminescence (PL), and time-resolved PL (TRPL) measurements were performed. The PL emissions from quantum wells (QWs) of blue LED and QDs were enhanced by 10% and 32%, respectively, when the Ag NPs were included. The PL lifetimes of QWs and QDs were reduced by 10 and 6 times, respectively, compared to their initial states. Finite Difference Time Domain (FDTD) software and the perturbation method were used to simulate the PL measurements and variable separation. It was concluded that the coupling of QDs and QWs with localized surface plasmon (LSP) improves the external quantum efficiency (EQE) and enhances the spontaneous emission rate in both QWs and QDs. This paper provides a new idea for designing high-efficiency color conversion micro-LED.
{"title":"Simultaneous enhancements on emissions from quantum dot and quantum well by Ag nanoparticles for color conversion","authors":"C. Deng, Zhizhong Chen, Yifan Chen, Qian Sun, J. Nie, Z. Pan, Haodong Zhang, Boyan Dong, Yian Chen, Daqi Wang, Yuchen Li, Weihua Chen, Xiangning Kang, Qi Wang, Guoyi Zhang, B. Shen, Huijuan Wang, Fei Wang, Wei Wang, Zhongxiao Li","doi":"10.1088/1361-6641/ad3275","DOIUrl":"https://doi.org/10.1088/1361-6641/ad3275","url":null,"abstract":"\u0000 Quantum dots (QDs) have been paid much attention on the color conversion for light-emitting diode (LED) in micro-display recently. However, it is hard to achieve high color conversion efficiency in a thin QD layer. In this paper, we fabricated silver nanoparticles (Ag NPs) with radii ranging mostly from 25 to 35 nm on a blue LED with a peak wavelength of 450 nm, then spin-coated QDs with a peak wavelength of 565 nm. Scanning electron microscopy (SEM), cathodoluminescence (CL), photoluminescence (PL), and time-resolved PL (TRPL) measurements were performed. The PL emissions from quantum wells (QWs) of blue LED and QDs were enhanced by 10% and 32%, respectively, when the Ag NPs were included. The PL lifetimes of QWs and QDs were reduced by 10 and 6 times, respectively, compared to their initial states. Finite Difference Time Domain (FDTD) software and the perturbation method were used to simulate the PL measurements and variable separation. It was concluded that the coupling of QDs and QWs with localized surface plasmon (LSP) improves the external quantum efficiency (EQE) and enhances the spontaneous emission rate in both QWs and QDs. This paper provides a new idea for designing high-efficiency color conversion micro-LED.","PeriodicalId":21585,"journal":{"name":"Semiconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140253842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Computing in-memory (CiM) is an alternative to von-Neumann architectures for energy efficient AI edge computing architectures with CMOS scaling. Approximate computing in-memory (ACiM) techniques have also been recently proposed to further increase the energy efficiency of such architectures. In the first part of the work, a Negative Capacitance FET (NCFET) based 6T-SRAM CiM accurate full adder has been proposed, designed and performance benchmarked with equivalent baseline 40nm CMOS design. Due to the steep slope characteristics of NCFET, at an increased ferroelectric layer thickness, Tfe of 3nm, the energy consumption of the proposed accurate NCFET based CiM design is ~82.48% lower in comparison to the conventional/Non CiM full adder design and ~ 85.27% lower energy consumption in comparison to the equivalent baseline CMOS CiM accurate full adder design at VDD = 0.5V. This work further proposes a reconfigurable computing in-memory NCFET 6T-SRAM full adder design (the design which can operate both in accurate and approximate modes of operation). NCFET 6T-SRAM reconfigurable full adder design in accurate mode has ~4.19x lower energy consumption and ~4.47x lower energy consumption in approximation mode when compared to the baseline 40nm CMOS design at VDD=0.5V, making NCFET based approximate CiM adder designs preferable for energy efficient AI edge CiM based computing architectures for DNN processing.
{"title":"Computing in-memory reconfigurable (accurate/approximate) adder design with negative capacitance FET 6T-SRAM for energy efficient AI edge devices","authors":"Venu Birudu, Tirumalarao Kadiyam, Koteswararao Penumalli, Sivasankar Yellampalli, Ramesh Vaddi","doi":"10.1088/1361-6641/ad3273","DOIUrl":"https://doi.org/10.1088/1361-6641/ad3273","url":null,"abstract":"\u0000 Computing in-memory (CiM) is an alternative to von-Neumann architectures for energy efficient AI edge computing architectures with CMOS scaling. Approximate computing in-memory (ACiM) techniques have also been recently proposed to further increase the energy efficiency of such architectures. In the first part of the work, a Negative Capacitance FET (NCFET) based 6T-SRAM CiM accurate full adder has been proposed, designed and performance benchmarked with equivalent baseline 40nm CMOS design. Due to the steep slope characteristics of NCFET, at an increased ferroelectric layer thickness, Tfe of 3nm, the energy consumption of the proposed accurate NCFET based CiM design is ~82.48% lower in comparison to the conventional/Non CiM full adder design and ~ 85.27% lower energy consumption in comparison to the equivalent baseline CMOS CiM accurate full adder design at VDD = 0.5V. This work further proposes a reconfigurable computing in-memory NCFET 6T-SRAM full adder design (the design which can operate both in accurate and approximate modes of operation). NCFET 6T-SRAM reconfigurable full adder design in accurate mode has ~4.19x lower energy consumption and ~4.47x lower energy consumption in approximation mode when compared to the baseline 40nm CMOS design at VDD=0.5V, making NCFET based approximate CiM adder designs preferable for energy efficient AI edge CiM based computing architectures for DNN processing.","PeriodicalId":21585,"journal":{"name":"Semiconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140253620","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-11DOI: 10.1088/1361-6641/ad3274
Yihang Qiu, Li Wei
A novel GaN trench gate vertical MOSFET (PSGT-MOSFET) with a double-shield structure composed of a separated gate (SG) and a p-type shielding layer (P_shield) is proposed and investigated. The p-type shielding layer (P_shield) is positioned within the drift region, which can suppress the electric field peak at the bottom of the trench during the off state. This helps to prevent premature breakdown of the gate oxide layer. Additionally, the presence of P_shield enables the device to have adaptive voltage withstand characteristics. The separated gate (SG) can convert a portion of gate to- -drain capacitance (Cgd) into drain-to-source capacitance (Cds), significantly reducing the gate-to-drain charge of the device. This improvement in charge distribution helps enhance the switching characteristics of the device. Later, the impact of the position and length of the p-type shielding layer (P_shield) on the breakdown voltage (BV) and specific on-resistance (Ron_sp) was studied. The influence of the position and length of the separated gate (SG) on gate charge (Qgd) and breakdown voltage was also investigated. Through TCAD simulations, the parameters of P_shield and SG were optimized. Compared to conventional GaN TG-MOSFET with the same structural parameters, the gate charge was reduced by 88%. In addition, this paper also discusses the principle of adaptive voltage withstand in PSGT-MOSFET.
本文提出并研究了一种新型氮化镓沟槽栅垂直 MOSFET（PSGT-MOSFET），它具有由分离栅极（SG）和 p 型屏蔽层（P_shield）组成的双屏蔽结构。p 型屏蔽层 (P_shield) 位于漂移区内，可以抑制关断状态下沟槽底部的电场峰值。这有助于防止栅极氧化层过早击穿。此外，P_shield 的存在还能使器件具有自适应耐压特性。分离栅极 (SG) 可以将部分栅极-漏极电容 (Cgd) 转换为漏极-源极电容 (Cds)，从而显著降低器件的栅极-漏极电荷。电荷分布的改善有助于提高器件的开关特性。随后，研究了 p 型屏蔽层（P_shield）的位置和长度对击穿电压（BV）和比导通电阻（Ron_sp）的影响。此外，还研究了分离栅极（SG）的位置和长度对栅极电荷（Qgd）和击穿电压的影响。通过 TCAD 仿真，对 P_shield 和 SG 的参数进行了优化。与具有相同结构参数的传统 GaN TG-MOSFET 相比，栅极电荷减少了 88%。此外，本文还讨论了 PSGT-MOSFET 的自适应电压承受原理。
{"title":"The GaN trench MOSFET with adaptive voltage tolerance achieved through a dual-shielding structure","authors":"Yihang Qiu, Li Wei","doi":"10.1088/1361-6641/ad3274","DOIUrl":"https://doi.org/10.1088/1361-6641/ad3274","url":null,"abstract":"\u0000 A novel GaN trench gate vertical MOSFET (PSGT-MOSFET) with a double-shield structure composed of a separated gate (SG) and a p-type shielding layer (P_shield) is proposed and investigated. The p-type shielding layer (P_shield) is positioned within the drift region, which can suppress the electric field peak at the bottom of the trench during the off state. This helps to prevent premature breakdown of the gate oxide layer. Additionally, the presence of P_shield enables the device to have adaptive voltage withstand characteristics. The separated gate (SG) can convert a portion of gate to- -drain capacitance (Cgd) into drain-to-source capacitance (Cds), significantly reducing the gate-to-drain charge of the device. This improvement in charge distribution helps enhance the switching characteristics of the device. Later, the impact of the position and length of the p-type shielding layer (P_shield) on the breakdown voltage (BV) and specific on-resistance (Ron_sp) was studied. The influence of the position and length of the separated gate (SG) on gate charge (Qgd) and breakdown voltage was also investigated. Through TCAD simulations, the parameters of P_shield and SG were optimized. Compared to conventional GaN TG-MOSFET with the same structural parameters, the gate charge was reduced by 88%. In addition, this paper also discusses the principle of adaptive voltage withstand in PSGT-MOSFET.","PeriodicalId":21585,"journal":{"name":"Semiconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140251387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-08DOI: 10.1088/1361-6641/ad2b07
Kihwan Choi, James Jungho Pak
In this study, a solution-processed bilayer structure ZrO2/SnO2 resistive switching (RS) random access memory (RRAM) is presented for the first time. The precursors of SnO2 and ZrO2 are Tin(Ⅱ) acetylacetonate (Sn(AcAc)2) and zirconium acetylacetonate (Zr(C5H7O2)4), respectively. The top electrode was deposited with Ti using an E-beam evaporator, and the bottom electrode used an indium–tin–oxide glass wafer. We created three devices: SnO2 single-layer, ZrO2 single-layer, and ZrO2/SnO2 bilayer devices, to compare RS characteristics such as the I–V curve and endurance properties. The SnO2 and ZrO2 single-layer devices showed on/off ratios of approximately 2 and 51, respectively, along with endurance switching cycles exceeding 50 and 100 DC cycles. The bilayer device attained stable RS characteristics over 120 DC endurance switching cycles and increased on/off ratio ∼2.97 × 102. Additionally, the ZrO2/SnO2 bilayer bipolar switching mechanism was explained by considering the Gibbs free energy (ΔGo) difference in the ZrO2 and SnO2 layers, where the formation and rupture of conductive filaments were caused by oxygen vacancies. The disparity in the concentration of oxygen vacancies, as indicated by the Gibbs free energy difference between ZrO2 (ΔGo = −1100 kJ mol−1) and SnO2 (ΔGo = −842.91 kJ mol−1) implied that ZrO2 exhibited a higher abundance of oxygen vacancies compared to SnO2, resulting in improved endurance and on/off ratio. X-ray photoelectron spectroscopy analyzed oxygen vacancies in ZrO2 and SnO2 thin films. The resistance switching characteristics were improved due to the bilayer structure, which combines a higher oxygen vacancy concentration in one layer with a lower oxygen vacancy concentration in the switching layer. This configuration reduces the escape of oxygen vacancies to the electrode during RS.
{"title":"Improved resistive switching characteristics of solution processed ZrO2/SnO2 bilayer RRAM via oxygen vacancy differential","authors":"Kihwan Choi, James Jungho Pak","doi":"10.1088/1361-6641/ad2b07","DOIUrl":"https://doi.org/10.1088/1361-6641/ad2b07","url":null,"abstract":"In this study, a solution-processed bilayer structure ZrO<sub>2</sub>/SnO<sub>2</sub> resistive switching (RS) random access memory (RRAM) is presented for the first time. The precursors of SnO<sub>2</sub> and ZrO<sub>2</sub> are Tin(Ⅱ) acetylacetonate (Sn(AcAc)<sub>2</sub>) and zirconium acetylacetonate (Zr(C<sub>5</sub>H<sub>7</sub>O<sub>2</sub>)<sub>4</sub>), respectively. The top electrode was deposited with Ti using an E-beam evaporator, and the bottom electrode used an indium–tin–oxide glass wafer. We created three devices: SnO<sub>2</sub> single-layer, ZrO<sub>2</sub> single-layer, and ZrO<sub>2</sub>/SnO<sub>2</sub> bilayer devices, to compare RS characteristics such as the <italic toggle=\"yes\">I</italic>–<italic toggle=\"yes\">V</italic> curve and endurance properties. The SnO<sub>2</sub> and ZrO<sub>2</sub> single-layer devices showed on/off ratios of approximately 2 and 51, respectively, along with endurance switching cycles exceeding 50 and 100 DC cycles. The bilayer device attained stable RS characteristics over 120 DC endurance switching cycles and increased on/off ratio ∼2.97 × 10<sup>2</sup>. Additionally, the ZrO<sub>2</sub>/SnO<sub>2</sub> bilayer bipolar switching mechanism was explained by considering the Gibbs free energy (Δ<italic toggle=\"yes\">G</italic>\u0000<sup>o</sup>) difference in the ZrO<sub>2</sub> and SnO<sub>2</sub> layers, where the formation and rupture of conductive filaments were caused by oxygen vacancies. The disparity in the concentration of oxygen vacancies, as indicated by the Gibbs free energy difference between ZrO<sub>2</sub> (Δ<italic toggle=\"yes\">G</italic>\u0000<sup>o</sup> = −1100 kJ mol<sup>−1</sup>) and SnO<sub>2</sub> (Δ<italic toggle=\"yes\">G</italic>\u0000<sup>o</sup> = −842.91 kJ mol<sup>−1</sup>) implied that ZrO<sub>2</sub> exhibited a higher abundance of oxygen vacancies compared to SnO<sub>2</sub>, resulting in improved endurance and on/off ratio. X-ray photoelectron spectroscopy analyzed oxygen vacancies in ZrO<sub>2</sub> and SnO<sub>2</sub> thin films. The resistance switching characteristics were improved due to the bilayer structure, which combines a higher oxygen vacancy concentration in one layer with a lower oxygen vacancy concentration in the switching layer. This configuration reduces the escape of oxygen vacancies to the electrode during RS.","PeriodicalId":21585,"journal":{"name":"Semiconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140314455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-08DOI: 10.1088/1361-6641/ad2a7f
Lijian Guo, Feng Zhou, Weizong Xu, Fangfang Ren, Dong Zhou, Dunjun Chen, Rong Zhang, Youdou Zheng, Hai Lu
Bonding pad over active (BPOA) layout, which stacks traditional horizontal structure pad electrodes vertically above the active area, is an area-effective device architecture and packaging-enabled solution for GaN-based high electron mobility transistors (HEMTs). In this work, the dynamic switching and electric field distribution of such layout, as well as associated capacitance–voltage and trapping characteristics, are comprehensively studied on D-mode GaN-on-sapphire HEMT by performing numerical simulations. In terms of different pad electrodes covering the active area, BPOA is composed of various structures such as gate-related and drain-related BPOAs (i.e. G-BPOA and D-BPOA), among which G-BPOA exhibits inferior switching characteristics due to the additional introduction of Miller capacitance that prolongs the device switching, while breakdown voltage of D-BPOA is 400–900 V lower than other BPOA counterparts due to the interplay between D-BPOA and the drain electrode. Furthermore, the effects of trap capture cross section and trap density on switching characteristics are evaluated. These results highlight the differences in electrical characteristics of various structures within the BPOA layout, and provide valuable insights into BPOA device design and performance improvement.
{"title":"Insights into dynamic switching behavior and electric field distribution of depletion-mode GaN HEMT with bonding pad over active layout","authors":"Lijian Guo, Feng Zhou, Weizong Xu, Fangfang Ren, Dong Zhou, Dunjun Chen, Rong Zhang, Youdou Zheng, Hai Lu","doi":"10.1088/1361-6641/ad2a7f","DOIUrl":"https://doi.org/10.1088/1361-6641/ad2a7f","url":null,"abstract":"Bonding pad over active (BPOA) layout, which stacks traditional horizontal structure pad electrodes vertically above the active area, is an area-effective device architecture and packaging-enabled solution for GaN-based high electron mobility transistors (HEMTs). In this work, the dynamic switching and electric field distribution of such layout, as well as associated capacitance–voltage and trapping characteristics, are comprehensively studied on D-mode GaN-on-sapphire HEMT by performing numerical simulations. In terms of different pad electrodes covering the active area, BPOA is composed of various structures such as gate-related and drain-related BPOAs (i.e. G-BPOA and D-BPOA), among which G-BPOA exhibits inferior switching characteristics due to the additional introduction of Miller capacitance that prolongs the device switching, while breakdown voltage of D-BPOA is 400–900 V lower than other BPOA counterparts due to the interplay between D-BPOA and the drain electrode. Furthermore, the effects of trap capture cross section and trap density on switching characteristics are evaluated. These results highlight the differences in electrical characteristics of various structures within the BPOA layout, and provide valuable insights into BPOA device design and performance improvement.","PeriodicalId":21585,"journal":{"name":"Semiconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140316846","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-07DOI: 10.1088/1361-6641/ad3111
Hyunjin Park, Jimin Kwon, Jihyung Seo, Kiho Kim, Yun Ho Kim, Sungjune Jung
In this work, a fully flexible graphene field-effect transistor with high carrier mobility is reported. Patterned high-quality and uniform single-layer graphene films are successfully realized by combining the selective growth on a patterned copper foil and the direct transfer method to minimize degradation factors. The selectively grown single-layer graphene is directly transferred to the target substrate through the deposition of poly-para-xylylene (Parylene) C. The quality of the graphene films is confirmed by Raman spectroscopy. The analysis reveals that the use of Parylene C as the substrate, gate dielectric, and encapsulation layer has the advantage of reducing the scattering by the optical phonons and charge puddles. The estimated residual carrier density is 1.72 × 1011 cm−2, and the intrinsic hole and electron carrier mobilities are found to be as high as 10260 and 10010 cm2·V−1·s−1, respectively. This study can pave the way for the development and mass production of high-performance and fully flexible graphene electronics.
{"title":"Flexible field-effect transistors with high-quality and uniform single-layer graphene for high mobility","authors":"Hyunjin Park, Jimin Kwon, Jihyung Seo, Kiho Kim, Yun Ho Kim, Sungjune Jung","doi":"10.1088/1361-6641/ad3111","DOIUrl":"https://doi.org/10.1088/1361-6641/ad3111","url":null,"abstract":"\u0000 In this work, a fully flexible graphene field-effect transistor with high carrier mobility is reported. Patterned high-quality and uniform single-layer graphene films are successfully realized by combining the selective growth on a patterned copper foil and the direct transfer method to minimize degradation factors. The selectively grown single-layer graphene is directly transferred to the target substrate through the deposition of poly-para-xylylene (Parylene) C. The quality of the graphene films is confirmed by Raman spectroscopy. The analysis reveals that the use of Parylene C as the substrate, gate dielectric, and encapsulation layer has the advantage of reducing the scattering by the optical phonons and charge puddles. The estimated residual carrier density is 1.72 × 1011 cm−2, and the intrinsic hole and electron carrier mobilities are found to be as high as 10260 and 10010 cm2·V−1·s−1, respectively. This study can pave the way for the development and mass production of high-performance and fully flexible graphene electronics.","PeriodicalId":21585,"journal":{"name":"Semiconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140259747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-07DOI: 10.1088/1361-6641/ad3113
V. Mughnetsyan, A. Manaselyan, Ashot Movsisyan, A. Kirakosyan
On the basis of the theory, developed for the dielectric function of atomic thin layer insulating materials (P. Cudazzo et al., PRB 84, 085406 (2011)) some characteristics of transition metal dichalcogenides’ monolayers are calculated in the frame of variational method. This method initially has been designed to work for very weak or strong magnetic fields, but it is also in very good agreement with numerical results obtained for intermediate magnetic fields. The expressions of the energy and the effective radius of the ground impurity state depending on the effective screening parameter of the problem are obtained both without and with magnetic fields.
{"title":"Effect of two-dimensional non-local screening on characteristics of transition metal dichalcogenide monolayers","authors":"V. Mughnetsyan, A. Manaselyan, Ashot Movsisyan, A. Kirakosyan","doi":"10.1088/1361-6641/ad3113","DOIUrl":"https://doi.org/10.1088/1361-6641/ad3113","url":null,"abstract":"\u0000 On the basis of the theory, developed for the dielectric function of atomic thin layer insulating materials (P. Cudazzo et al., PRB 84, 085406 (2011)) some characteristics of transition metal dichalcogenides’ monolayers are calculated in the frame of variational method. This method initially has been designed to work for very weak or strong magnetic fields, but it is also in very good agreement with numerical results obtained for intermediate magnetic fields. The expressions of the energy and the effective radius of the ground impurity state depending on the effective screening parameter of the problem are obtained both without and with magnetic fields.","PeriodicalId":21585,"journal":{"name":"Semiconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140258597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-07DOI: 10.1088/1361-6641/ad2d62
Takahiro Fujisawa, Nan Hu, Tomoki Kojima, Takashi Egawa, Makoto Miyoshi
We investigated the GaInN-based photoelectric transducers (PTs) aiming at the application to optical wireless power transmission systems. A PT device structure with Ga0.9In0.1N multiple-quantum-wells (MQWs) as a light absorption layer was grown on a free-standing GaN substrate by metalorganic chemical vapor deposition and subjected to the device fabrication. The PT performance was evaluated via the two-terminal current-density vs. voltage characteristics taken under a monochromatic light illumination. The fabricated PT devices exhibited a high open-circuit voltage of approximately 2.3 V and a high shunt resistance of 41 kΩcm2, thanks to its good material qualities. In addition, its surface reflection was markedly suppressed by an adoption of a wet surface treatment and an anti-reflection coating, resulting in a high external quantum efficiency of 90% and a high short-circuit current density of 1.4 mAcm−2. Through the above investigation, a high power-conversion efficiency as great as 43.7% was achieved for the GaInN MQW PTs at a light illumination with 390 nm in wavelength and 5 mWcm−2 in optical power density.
{"title":"Over 43%-power-efficiency GaInN-based photoelectric transducer on free-standing GaN substrate for optical wireless power transmission system","authors":"Takahiro Fujisawa, Nan Hu, Tomoki Kojima, Takashi Egawa, Makoto Miyoshi","doi":"10.1088/1361-6641/ad2d62","DOIUrl":"https://doi.org/10.1088/1361-6641/ad2d62","url":null,"abstract":"We investigated the GaInN-based photoelectric transducers (PTs) aiming at the application to optical wireless power transmission systems. A PT device structure with Ga<sub>0.9</sub>In<sub>0.1</sub>N multiple-quantum-wells (MQWs) as a light absorption layer was grown on a free-standing GaN substrate by metalorganic chemical vapor deposition and subjected to the device fabrication. The PT performance was evaluated via the two-terminal current-density vs. voltage characteristics taken under a monochromatic light illumination. The fabricated PT devices exhibited a high open-circuit voltage of approximately 2.3 V and a high shunt resistance of 41 kΩcm<sup>2</sup>, thanks to its good material qualities. In addition, its surface reflection was markedly suppressed by an adoption of a wet surface treatment and an anti-reflection coating, resulting in a high external quantum efficiency of 90% and a high short-circuit current density of 1.4 mAcm<sup>−2</sup>. Through the above investigation, a high power-conversion efficiency as great as 43.7% was achieved for the GaInN MQW PTs at a light illumination with 390 nm in wavelength and 5 mWcm<sup>−2</sup> in optical power density.","PeriodicalId":21585,"journal":{"name":"Semiconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140314606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Organic light-emitting diodes (OLEDs) have become one of the mainstream lighting and display technologies. The vacuum thermal evaporation is the most widely adopted method for the preparation of organic and metal materials of OLEDs. The thermal deposition of the commonly used silver (Ag) and aluminum (Al) electrodes requires high temperature and long time, which greatly increases the cost of the fabricating process. Therefore, we selected silver oxide (Ag2O) powder instead of Ag pellets as the precursor for evaporating Ag electrodes. Compared to Ag pellets and Al wires, Ag2O-based Ag electrode need lower evaporation temperature and shorter preheating time. In addition, the agglomeration phenomenon on the surface of the Ag2O-based Ag film is prevented, which also increases the carrier concentration of Ag electrode. Moreover, by doping bathophenanthroline (Bphen) in Ag2O powders, the phenanthroline-metal (Bphen-Ag) complexes with higher electron mobility and stronger electron injecting ability can be achieved. We applied Ag2O-based Ag electrode and 10 wt.% Ag2O-based Ag:Bphen as electron injection layer to achieve high-efficiency red phosphorescent inverted OLEDs, with the maximum current efficiency, external quantum efficiency, and power efficiency of 17.79 cd A−1, 20.71%, and 12.14 lm W−1, respectively. This method provides a new strategy for preparing highly efficient inverted red OLED devices.
{"title":"Study on low-temperature evaporation of Ag2O-based Ag electrode and electron injection layer and their application in OLEDs","authors":"Yachen Xu, Jialu Gu, Lulu Zhou, Bingjia Zhao, Yangyang Zhu, Wei Shi, Bin Wei","doi":"10.1088/1361-6641/ad2d63","DOIUrl":"https://doi.org/10.1088/1361-6641/ad2d63","url":null,"abstract":"Organic light-emitting diodes (OLEDs) have become one of the mainstream lighting and display technologies. The vacuum thermal evaporation is the most widely adopted method for the preparation of organic and metal materials of OLEDs. The thermal deposition of the commonly used silver (Ag) and aluminum (Al) electrodes requires high temperature and long time, which greatly increases the cost of the fabricating process. Therefore, we selected silver oxide (Ag<sub>2</sub>O) powder instead of Ag pellets as the precursor for evaporating Ag electrodes. Compared to Ag pellets and Al wires, Ag<sub>2</sub>O-based Ag electrode need lower evaporation temperature and shorter preheating time. In addition, the agglomeration phenomenon on the surface of the Ag<sub>2</sub>O-based Ag film is prevented, which also increases the carrier concentration of Ag electrode. Moreover, by doping bathophenanthroline (Bphen) in Ag<sub>2</sub>O powders, the phenanthroline-metal (Bphen-Ag) complexes with higher electron mobility and stronger electron injecting ability can be achieved. We applied Ag<sub>2</sub>O-based Ag electrode and 10 wt.% Ag<sub>2</sub>O-based Ag:Bphen as electron injection layer to achieve high-efficiency red phosphorescent inverted OLEDs, with the maximum current efficiency, external quantum efficiency, and power efficiency of 17.79 cd A<sup>−1</sup>, 20.71%, and 12.14 lm W<sup>−1</sup>, respectively. This method provides a new strategy for preparing highly efficient inverted red OLED devices.","PeriodicalId":21585,"journal":{"name":"Semiconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140314454","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-07DOI: 10.1088/1361-6641/ad3114
Qing Fan, Lixiang Wang, Xu Gao, Yuchao Yan, Ming Li, Zhu Jin, Yanjun Fang, Ning Xia, Hui Zhang, Deren Yang
As a booming semiconductor material, -Ga2O3 with an ultra-wide bandgap of 4.8 eV exhibits several advantages in scintillator with high stability and low self-absorption. To further improve the scintillation performance, we grown unintentionally doped (UID), Cu-, Fe-, Mg-, and Si-doped -Ga2O3 substrates by the floating zone (FZ) method. The 0.1 mol% Cu-doped -Ga2O3 exhibits the highest light yield of 6975 ph/MeV with a good linear response, which represents better predictable and stable for the input X-ray energy. Photoluminescence (PL) shows peak emission around 425 nm under the excitation of 254 nm. All the results shows that the Cu-doped -Ga2O3 is an effective scintillator with excellent light yield, which provides an alternative way for the high-performance ionizing radiation detectors.
作为一种蓬勃发展的半导体材料，-Ga2O3 具有 4.8 eV 的超宽带隙，在闪烁体中具有高稳定性和低自吸收等优点。为了进一步提高闪烁性能，我们采用浮区（FZ）法生长了无意掺杂（UID）、铜掺杂、铁掺杂、镁掺杂和硅掺杂的 -Ga2O3 衬底。掺杂 0.1 mol% Cu 的 -Ga2O3 显示出最高的光产率 6975 ph/MeV，具有良好的线性响应，对输入的 X 射线能量具有更好的可预测性和稳定性。在 254 nm 的激发下，光致发光（PL）在 425 nm 附近达到发射峰值。所有这些结果表明，掺铜的 -Ga2O3 是一种有效的闪烁体，具有出色的光产率，为高性能电离辐射探测器提供了另一种途径。
{"title":"Enhanced scintillation performance of Cu-doped β-Ga2O3 single crystals grown by floating-zone method","authors":"Qing Fan, Lixiang Wang, Xu Gao, Yuchao Yan, Ming Li, Zhu Jin, Yanjun Fang, Ning Xia, Hui Zhang, Deren Yang","doi":"10.1088/1361-6641/ad3114","DOIUrl":"https://doi.org/10.1088/1361-6641/ad3114","url":null,"abstract":"\u0000 As a booming semiconductor material, -Ga2O3 with an ultra-wide bandgap of 4.8 eV exhibits several advantages in scintillator with high stability and low self-absorption. To further improve the scintillation performance, we grown unintentionally doped (UID), Cu-, Fe-, Mg-, and Si-doped -Ga2O3 substrates by the floating zone (FZ) method. The 0.1 mol% Cu-doped -Ga2O3 exhibits the highest light yield of 6975 ph/MeV with a good linear response, which represents better predictable and stable for the input X-ray energy. Photoluminescence (PL) shows peak emission around 425 nm under the excitation of 254 nm. All the results shows that the Cu-doped -Ga2O3 is an effective scintillator with excellent light yield, which provides an alternative way for the high-performance ionizing radiation detectors.","PeriodicalId":21585,"journal":{"name":"Semiconductor Science and Technology","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140260250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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