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420nm thick CH_3NH_3PbI_(3-x)Br_x capping layers for efficient TiO_2 nanorod array perovskite solar cells
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作者 李龙 史成武 +3 位作者 邓新莲 王艳青 肖冠南 倪玲玲 《Chinese Physics B》 SCIE EI CAS CSCD 2018年第1期104-108,共5页
The rutile TiO2 nanorod arrays with 240 nm in length, 30 nm in diameter, and 420 btm 2 in areal density were prepared by the hydrothermal method to replace the typical 200-300 nm thick mesoporous TiO2 thin films in pe... The rutile TiO2 nanorod arrays with 240 nm in length, 30 nm in diameter, and 420 btm 2 in areal density were prepared by the hydrothermal method to replace the typical 200-300 nm thick mesoporous TiO2 thin films in perovskite solar cells. The CH3NH3PbI3 xBrx capping layers with different thicknesses were obtained on the TiO2 nanorod arrays using different concentration PbI2.DMSO complex precursor solutions in DMF and the photovoltaic performances of the corresponding solar cells were compared. The perovskite solar cells based on 240 nm long TiO2 nanorod arrays and 420 nm thick CH3NH3PbI3 xBrx capping layers showed the best photoelectric conversion efficiency (PCE) of 15.56% and the average PCE of 14.93 ± 0.63% at the relative humidity of 50%-54% under the illumination of simulated AM 1.5 sunlight (100 mW.cm-2). 展开更多
关键词 rutile TiO2 nanorod array CH3NH3PbI3 xBrx capping layer perovskite solar cell
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Study on influences of TiN capping layer on time-dependent dielectric breakdown characteristic of ultra-thin EOT high-k metal gate NMOSFET with kMC TDDB simulations
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作者 徐昊 杨红 +11 位作者 罗维春 徐烨峰 王艳蓉 唐波 王文武 祁路伟 李俊峰 闫江 朱慧珑 赵超 陈大鹏 叶甜春 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第8期347-351,共5页
The thickness effect of the TiN capping layer on the time dependent dielectric breakdown(TDDB) characteristic of ultra-thin EOT high-k metal gate NMOSFET is investigated in this paper.Based on experimental results,i... The thickness effect of the TiN capping layer on the time dependent dielectric breakdown(TDDB) characteristic of ultra-thin EOT high-k metal gate NMOSFET is investigated in this paper.Based on experimental results,it is found that the device with a thicker TiN layer has a more promising reliability characteristic than that with a thinner TiN layer.From the charge pumping measurement and secondary ion mass spectroscopy(SIMS) analysis,it is indicated that the sample with the thicker TiN layer introduces more Cl passivation at the IL/Si interface and exhibits a lower interface trap density.In addition,the influences of interface and bulk trap density ratio Nit/Not are studied by TDDB simulations through combining percolation theory and the kinetic Monte Carlo(kMC) method.The lifetime reduction and Weibull slope lowering are explained by interface trap effects for TiN capping layers with different thicknesses. 展开更多
关键词 high-k metal gate TiN capping layer TDDB interface trap density
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Effects of the strain relaxation of an AlGaN barrier layer induced by various cap layers on the transport properties in AlGaN/GaN heterostructures
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作者 刘子扬 张进成 +5 位作者 段焕涛 薛军帅 林志宇 马俊彩 薛晓咏 郝跃 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第9期425-429,共5页
The strain relaxation of an A1GaN barrier layer may be influenced by a thin cap layer above, and affects the transport properties of A1GaN/GaN heterostructures. Compared with the slight strain relaxation found in A1Ga... The strain relaxation of an A1GaN barrier layer may be influenced by a thin cap layer above, and affects the transport properties of A1GaN/GaN heterostructures. Compared with the slight strain relaxation found in A1GaN barrier layer without cap layer, it is found that a thin cap layer can induce considerable changes of strain state in the A1GaN barrier layer. The degree of relaxation of the A1GaN layer significantly influences the transport properties of the two-dimensional electron gas (2DEG) in A1GaN/GaN heterostructures. It is observed that electron mobility decreases with the increasing degree of relaxation of the A1GaN barrier, which is believed to be the main cause of the deterioration of crystalline quality and morphology on the A1GaN/GaN interface. On the other hand, both GaN and A1N cap layers lead to a decrease in 2DEC density. The reduction of 2DEG caused by the GaN cap layer may be attributed to the additional negative polarization charges formed at the interface between CaN and A1GaN, while the reduction of the piezoelectric effect in the A1GaN layer results in the decrease of 2DEC density in the case of A1N cap layer. 展开更多
关键词 cap layer strain relaxation A1GAN/GAN transport properties
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Influence of an Fe cap layer on the structural and magnetic properties of Fe_(49)Pt_(51)/Fe bi-layers
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作者 段朝阳 马斌 +2 位作者 魏福林 张宗芝 金庆原 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第6期2565-2570,共6页
The influences of an Fe cap layer on the structural and magnetic properties of FePt/Fe bi-layers are investigated. Compared with single FePt alloy films, a thin Fe layer can affect the crystalline orientation and impr... The influences of an Fe cap layer on the structural and magnetic properties of FePt/Fe bi-layers are investigated. Compared with single FePt alloy films, a thin Fe layer can affect the crystalline orientation and improve the chemical ordering of L10 FePt films. Moreover, the coercivity increases when a thin Fe layer covers the FePt layer. Beyond a critical thickness, however, the Fe cover layer quickens the magnetization reversal of Fe49Pt51/Fe bi-layers by their exchange coupling. 展开更多
关键词 Fe cap layer Llo FePt MAGNETISM
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Parameterization for the Depth of the Entrainment Zone above the Convectively Mixed Layer 被引量:3
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作者 孙鉴泞 蒋维楣 +1 位作者 陈子赟 袁仁民 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2005年第1期114-121,共8页
It has been noted that when the convective Richardson number Ri* is used to characterize the depth of the entrainment zone, various parameterization schemes can be obtained. This situation is often attributed to the i... It has been noted that when the convective Richardson number Ri* is used to characterize the depth of the entrainment zone, various parameterization schemes can be obtained. This situation is often attributed to the invalidity of parcel theory. However, evidence shows that the convective Richardson number Ri* might be an improper characteristic scaling parameter for the entrainment process. An attempt to use an innovative parameter to parameterize the entrainment-zone thickness has been made in this paper. Based on the examination of the data of water-tank experiments and atmospheric measurements, it is found that the total lapse rate of potential temperature across the entrainment zone is proportional to that of the capping inversion layer. Inserting this relationship into the so-called parcel theory, it thus gives a new parameterization scheme for the depth of the entrainment zone. This scheme includes the lapse rate of the capping inversion layer that plays an important role in the entrainment process. Its physical representation is reasonable. The new scheme gives a better ordering of the data measured in both water-tank and atmosphere as compared with the traditional method using Ri*. These indicate that the parcel theory can describe the entrainment process suitably and that the new parameter is better than Ri*. 展开更多
关键词 convectively mixed layer the depth of the entrainment zone capping inversion layer parameterization scheme parcel theory
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The exciton-longitudinal-optical-phonon coupling in InGaN/GaN single quantum wells with various cap layer thicknesses 被引量:1
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作者 胡晓龙 张江勇 +2 位作者 尚景智 刘文杰 张保平 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第11期653-657,共5页
This paper studies the exciton-longitudinal-optical-phonon coupling in InGaN/GaN single quantum wells with various cap layer thicknesses by low temperature photoluminescence (PL) measurements. With increasing cap la... This paper studies the exciton-longitudinal-optical-phonon coupling in InGaN/GaN single quantum wells with various cap layer thicknesses by low temperature photoluminescence (PL) measurements. With increasing cap layer thickness, the PL peak energy shifts to lower energy and the coupling strength between the exciton and longitudinal- optical (LO) phonon, described by Huang-Rhys factor, increases remarkably due to an enhancement of the internal electric field. With increasing excitation intensity, the zero-phonon peak shows a blueshift and the Huang-Rhys factor decreases. These results reveal that there is a large built-in electric field in the well layer and the exciton-LO-phonon coupling is strongly affected by the thickness of the cap layer. 展开更多
关键词 exciton longitudinal-optical-phonon InGaN/GaN single quantum well GaN cap layer Huang-Rhys factor
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Effects of GaN cap layer thickness on an AlN/GaN heterostructure
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作者 赵景涛 林兆军 +3 位作者 栾崇彪 吕元杰 冯志宏 杨铭 《Chinese Physics B》 SCIE EI CAS CSCD 2014年第12期404-407,共4页
In this study, we investigate the effects of Ga N cap layer thickness on the two-dimensional electron gas(2DEG)electron density and 2DEG electron mobility of Al N/Ga N heterostructures by using the temperature-depen... In this study, we investigate the effects of Ga N cap layer thickness on the two-dimensional electron gas(2DEG)electron density and 2DEG electron mobility of Al N/Ga N heterostructures by using the temperature-dependent Hall measurement and theoretical fitting method. The results of our analysis clearly indicate that the Ga N cap layer thickness of an Al N/Ga N heterostructure has influences on the 2DEG electron density and the electron mobility. For the Al N/Ga N heterostructures with a 3-nm Al N barrier layer, the optimized thickness of the Ga N cap layer is around 4 nm and the strained a-axis lattice constant of the Al N barrier layer is less than that of Ga N. 展开更多
关键词 AlN/Ga N heterostructure 2DEG Ga N cap layer a-axis lattice constant
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Design and simulation to improve the structural efficiency of green light emission of GaN/InGaN/AIGaN light emitting diode 被引量:1
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作者 Sakhawat HUSSAIN Tasnim ZERIN Md. Ashik KHAN 《Frontiers of Optoelectronics》 EI CSCD 2017年第4期370-377,共8页
This study considered the design of an efficient, high brightness polar InGaN/GaN light emitting diode (LED) structure with A1GaN capping layer for green light emission. The deposition of high In (〉 15%) composit... This study considered the design of an efficient, high brightness polar InGaN/GaN light emitting diode (LED) structure with A1GaN capping layer for green light emission. The deposition of high In (〉 15%) composition within InGaN quantum well (QW) has limitations when providing intense green light. To design an effective model for a highly efficient InGaN green LEDs, this study considered the compositions of indium and aluminum for InxGal xN QW and AlyGal yN cap layers, along with different layer thicknesses of well, barrier and cap. These structural properties significantly affect different properties. For example, these properties affect electric fields of layers, polarization, overall elastic stress energy and lattice parameter of the structure, emission wavelength, and intensity of the emitted light. Three models with different composition and layer thicknesses are simulated and analyzed to obtain green light with in-plane equilibrium lattice parameter close to GaN (3.189 A ) with the highest oscillator strength values. A structure model is obtained with an oscillator strength value of 1.18 × 10-1 and least in-plane equilibrium lattice constant of 3.218 A. This emitter can emit at a wavelength of 540 nm, which is the expected design for the fabrication of highly efficient, bright green LEDs. 展开更多
关键词 green light emitting diode (LED) latticeparameter oscillator strength InGaN quantum well (QW) A1GaN capping layer
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Optimization design on breakdown voltage of AlGaN/GaN high-electron mobility transistor
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作者 刘阳 柴常春 +2 位作者 史春蕾 樊庆扬 刘彧千 《Journal of Semiconductors》 EI CAS CSCD 2016年第12期40-44,共5页
Simulations are carried out to explore the possibility of achieving high breakdown voltage of Gain HEMT (high-electron mobility transistor). GaN cap layers with gradual increase in the doping concentration from 2 x ... Simulations are carried out to explore the possibility of achieving high breakdown voltage of Gain HEMT (high-electron mobility transistor). GaN cap layers with gradual increase in the doping concentration from 2 x 10^16 to 5 x 10^19 cm-3 of N-type and P-type cap are investigated, respectively. Simulation results show that HEMT with P-doped GaN cap layer shows more potential to achieve higher breakdown voltage than N-doped GaN cap layer under the same doping concentration. This is because the ionized net negative space charges in P-GaN cap layer could modulate the surface electric field which makes more contribution to RESURF effect. Furthermore, a novel GaN/A1GaN/GaN HEMT with P-doped GaN buried layer in GaN buffer between gate and drain electrode is proposed. It shows enhanced performance. The breakdown voltage of the proposed structure is 640 V which is increased by 12% in comparison to UID (un-intentionally doped) GaN/A1GaN/GaN HEMT. We calculated and analyzed the distribution of electrons' density. It is found that the depleted region is wider and electric field maximum value is induced at the left edge of buried layer. So the novel structure with P-doped GaN buried layer embedded in GaN buffer has the better improving characteristics of the power devices. 展开更多
关键词 GaN HEMT optimization design breakdown voltage cap layer
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