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Electronic and optical properties of GaN/AlN quantum dots with adjacent threading dislocations
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作者 叶寒 芦鹏飞 +4 位作者 俞重远 姚文杰 陈智辉 贾博雍 刘玉敏 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第4期375-380,共6页
We present a theory to simulate a coherent GaN QD with an adjacent pure edge threading dislocation by using a finite element method. The piezoelectric effects and the strain modified band edges are investigated in the... We present a theory to simulate a coherent GaN QD with an adjacent pure edge threading dislocation by using a finite element method. The piezoelectric effects and the strain modified band edges are investigated in the framework of multi-band κ · p theory to calculate the electron and the heavy hole energy levels. The linear optical absorption coefficients corresponding to the interband ground state transition are obtained via the density matrix approach and perturbation expansion method. The results indicate that the strain distribution of the threading dislocation affects the electronic structure. Moreover, the ground state transition behaviour is also influenced by the position of the adjacent threading dislocation. 展开更多
关键词 quantum dot threading dislocation electronic structure absorption efficiency
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Evaluation of threading dislocation density of strained Ge epitaxial layer by high resolution x-ray diffraction 被引量:1
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作者 苗渊浩 胡辉勇 +3 位作者 李鑫 宋建军 宣荣喜 张鹤鸣 《Chinese Physics B》 SCIE EI CAS CSCD 2017年第12期511-515,共5页
The analysis of threading dislocation density (TDD) in Ge-on-Si layer is critical for developing lasers, light emitting diodes (LEDs), photodetectors (PDs), modulators, waveguides, metal oxide semiconductor fiel... The analysis of threading dislocation density (TDD) in Ge-on-Si layer is critical for developing lasers, light emitting diodes (LEDs), photodetectors (PDs), modulators, waveguides, metal oxide semiconductor field effect transistors (MOSFETs), and also the integration of Si-based monolithic photonics. The TDD of Ge epitaxial layer is analyzed by etching or transmission electron microscope (TEM). However, high-resolution x-ray diffraction (HR-XRD) rocking curve provides an optional method to analyze the TDD in Ge layer. The theory model of TDD measurement from rocking curves was first used in zinc-blende semiconductors. In this paper, this method is extended to the case of strained Ge-on-Si layers. The HR-XRD 2θ/ω scan is measured and Ge (004) single crystal rocking curve is utilized to calculate the TDD in strained Ge epitaxial layer. The rocking curve full width at half maximum (FWHM) broadening by incident beam divergence of the instrument, crystal size, and curvature of the crystal specimen is subtracted. The TDDs of samples A and B are calculated to be 1.41108 cm-2 and 6.47108 cm-2, respectively. In addition, we believe the TDDs calculated by this method to be the averaged dislocation density in the Ge epitaxial layer. 展开更多
关键词 HR-XRD RPCVD threading dislocation density (TDD) etching pit density (EPD)
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Numerical investigation on threading dislocation bending with InAs/GaAs quantum dots
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作者 Guo-Feng Wu Jun Wang +8 位作者 Wei-Rong Chen Li-Na Zhu Yuan-Qing Yang Jia-Chen Li Chun-Yang Xiao Yong-Qing Huang Xiao-Min Ren Hai-Ming Ji Shuai Luo 《Chinese Physics B》 SCIE EI CAS CSCD 2021年第11期146-150,共5页
The threading dislocations(TDs)in GaAs/Si epitaxial layers due to the lattice mismatch seriously degrade the performance of the lasers grown on silicon.The insertion of InAs quantum dots(QDs)acting as dislocation filt... The threading dislocations(TDs)in GaAs/Si epitaxial layers due to the lattice mismatch seriously degrade the performance of the lasers grown on silicon.The insertion of InAs quantum dots(QDs)acting as dislocation filters is a pretty good alternative to solving this problem.In this paper,a finite element method(FEM)is proposed to calculate the critical condition for InAs/GaAs QDs bending TDs into interfacial misfit dislocations(MDs).Making a comparison of elastic strain energy between the two isolated systems,a reasonable result is obtained.The effect of the cap layer thickness and the base width of QDs on TD bending are studied,and the results show that the bending area ratio of single QD(the bending area divided by the area of the QD base)is evidently affected by the two factors.Moreover,we present a method to evaluate the bending capability of single-layer QDs and multi-layer QDs.For the QD with 24-nm base width and 5-nm cap layer thickness,taking the QD density of 10^(11) cm^(-2) into account,the bending area ratio of single-layer QDs(the area of bending TD divided by the area of QD layer)is about 38.71%.With inserting five-layer InAs QDs,the TD density decreases by 91.35%.The results offer the guidelines for designing the QD dislocation filters and provide an important step towards realizing the photonic integration circuits on silicon. 展开更多
关键词 InAs/GaAs quantum dots threading dislocation finite element method bending area
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Investigation of dislocations in 8° off-axis 4H-SiC epilayer
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作者 苗瑞霞 张玉明 +2 位作者 张义门 汤晓燕 盖庆丰 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第7期425-429,共5页
This paper reports that the etching morphology of dislocations in 8° off-axis 4H-SiC epilayer is observed by using a scanning electronic microscope. It is found that different types of dislocations correspond wit... This paper reports that the etching morphology of dislocations in 8° off-axis 4H-SiC epilayer is observed by using a scanning electronic microscope. It is found that different types of dislocations correspond with different densities and basal plane dislcation (BPD) array and threading edge dislocation (TED) pileup group lie along some certain crystal directions in the epilayer. It is concluded that the elastic energy of threading screw dislocations (TSDs) is highest and TEDs is lowest among these dislocations, so the density of TSDs is lower than TEDs. The BPDs can convert to TEDs but TSDs can only propagate into the epilyer in spite of the higher elastic energy than TEDs. The reason of the form of BPDs array in epilayer is that the big step along the basal plane caused by face defects blocked the upstream atoms, and TEDs pileup group is that the dislocations slide is blocked by dislocation groups in epilayer. 展开更多
关键词 elastic energy basal plane dislcations threding edge dislocations threading screw dislocations
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Evolution of microstructure, stress and dislocation of AlN thick film on nanopatterned sapphire substrates by hydride vapor phase epitaxy
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作者 王闯 高晓冬 +7 位作者 李迪迪 陈晶晶 陈家凡 董晓鸣 王晓丹 黄俊 曾雄辉 徐科 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第2期399-404,共6页
A crack-free AlN film with 4.5 μm thickness was grown on a 2-inch hole-type nano-patterned sapphire substrates(NPSSs) by hydride vapor phase epitaxy(HVPE). The coalescence, stress evolution, and dislocation annihilat... A crack-free AlN film with 4.5 μm thickness was grown on a 2-inch hole-type nano-patterned sapphire substrates(NPSSs) by hydride vapor phase epitaxy(HVPE). The coalescence, stress evolution, and dislocation annihilation mechanisms in the AlN layer have been investigated. The large voids located on the pattern region were caused by the undesirable parasitic crystallites grown on the sidewalls of the nano-pattern in the early growth stage. The coalescence of the c-plane AlN was hindered by these three-fold crystallites and the special triangle void appeared. The cross-sectional Raman line scan was used to characterize the change of stress with film thickness, which corresponds to the characteristics of different growth stages of AlN. Threading dislocations(TDs) mainly originate from the boundary between misaligned crystallites and the c-plane AlN and the coalescence of two adjacent c-plane AlN crystals, rather than the interface between sapphire and AlN. 展开更多
关键词 hydride vapor phase epitaxy(HVPE) ALN threading dislocations nano-patterned sapphire substrate
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Influence of double AlN buffer layers on the qualities of GaN films prepared by metal-organic chemical vapour deposition 被引量:2
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作者 林志宇 张进成 +7 位作者 周昊 李小刚 孟凡娜 张琳霞 艾姗 许晟瑞 赵一 郝跃 《Chinese Physics B》 SCIE EI CAS CSCD 2012年第12期403-407,共5页
In this paper we report that the GaN thin film is grown by metal-organic chemical vapour deposition on a sapphire (0001) substrate with double A1N buffer layers. The buffer layer consists of a low-temperature (LT)... In this paper we report that the GaN thin film is grown by metal-organic chemical vapour deposition on a sapphire (0001) substrate with double A1N buffer layers. The buffer layer consists of a low-temperature (LT) A1N layer and a high-temperature (HT) A1N layer that are grown at 600 ℃ and 1000 ℃, respectively. It is observed that the thickness of the LT-A1N layer drastically influences the quality of GaN thin film, and that the optimized 4.25-min-LT-A1N layer minimizes the dislocation density of GaN thin film. The reason for the improved properties is discussed in this paper. 展开更多
关键词 GAN A1N buffer layer metal-organic chemical vapour deposition threading dislocations
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Mosaic Structure Evolution in GaN Films with Annealing Time Grown by Metalorganic Chemical Vapour Deposition
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作者 陈志涛 徐科 +6 位作者 郭立平 杨志坚 潘尧波 苏月永 张酣 沈波 张国义 《Chinese Physics Letters》 SCIE CAS CSCD 2006年第5期1257-1260,共4页
We investigate mosaic structure evolution of GaN films annealed for a long time at 800℃ grown on sapphire substrates by metalorganic chemical vapour deposition by high-resolution x-ray diffraction. The result show th... We investigate mosaic structure evolution of GaN films annealed for a long time at 800℃ grown on sapphire substrates by metalorganic chemical vapour deposition by high-resolution x-ray diffraction. The result show that residual stress in GaN films is relaxed by generating edge-type threading dislocations (TDs) instead of screw-type TDs. Compared to as-grown GaN films, the annealed ones have larger mean twist angles corresponding to higher density of edge-type TDs but smaller mean tilt angles corresponding to lower density of screw-type TDs films. Due to the increased edge-type TD density, the lateral coherence lengths of the annealed GaN films also decrease. The results obtained from chemical etching experiment and grazing-incidence x-ray diffraction (GIXRD) also support the proposed structure evolution. 展开更多
关键词 threading dislocations DEFECT STRUCTURE EPITAXIAL GAN THIN-FILMS
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Preparation of AlN film grown on sputter-deposited and annealed AlN buffer layer via HVPE 被引量:1
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作者 Di-Di Li Jing-Jing Chen +4 位作者 Xu-Jun Su Jun Huang Mu-Tong Niu Jin-Tong Xu Ke Xu 《Chinese Physics B》 SCIE EI CAS CSCD 2021年第3期430-435,共6页
AlN films grown on sputter-deposited and annealed AlN buffer layer by high temperature hydride vapor phase epitaxy(HVPE)have been fabricated and structurally characterized.The crystalline quality and surface morpholog... AlN films grown on sputter-deposited and annealed AlN buffer layer by high temperature hydride vapor phase epitaxy(HVPE)have been fabricated and structurally characterized.The crystalline quality and surface morphology of as-grown AlN films with various V/III ratios were studied and compared.The XRD results showed that the crystalline quality of the AlN film could be optimized when the growth V/III ratio was 150.At the same time,the full width at half-maximum(FWHM)values of(0002)-and(10¯12)-plane were 64 arcsec and 648 arcsec,respectively.As revealed by AFM,the AlN films grown with higher V/III ratios of 150 and 300 exhibited apparent hillock-like surface structure due to the low density of screw threading dislocation(TD).The defects microstructure and strain field around the HVPE-AlN/sputtered-AlN/sapphire interfaces have been investigated by transmission electron microscopy(TEM)technique combined with geometric phase analysis(GPA).It was found that the screw TDs within AlN films intend to turn into loops or half-loops after originating from the AlN/sapphire interface,while the edge ones would bend first and then reacted with others within a region of 400 nm above the interface.Consequently,part of the edge TDs propagated to the surface vertically.The GPA analysis indicated that the voids extending from sapphire to HVPE-AlN layer were beneficial to relax the interfacial strain of the best quality AlN film grown with a V/III ratio of 150. 展开更多
关键词 hydride vapor phase epitaxy(HVPE) ALN threading dislocation(TD) SPUTTER-DEPOSITION
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The Characteristic of Threading Dislocation in Different Structures GaN Films Grown by MOCVD 被引量:1
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作者 Min Lu, Zilan Li, Zhijian Yang, Zonghui Li, Bei Zhang, Guoyi Zhang Research Center for Wide-Band Semiconductor materials, Peking University, Beijing 100871 P.R.China 《光学学报》 EI CAS CSCD 北大核心 2003年第S1期861-862,共2页
Three mechanisms to reduce threading dislocations(TDs) in GaN films as the epitaxial films grow thicker are suggested by SEM and
关键词 GAN on The Characteristic of threading Dislocation in Different Structures GaN Films Grown by MOCVD in of by
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Low threading dislocation density in GaN films grown on patterned sapphire substrates
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作者 梁萌 王国宏 +8 位作者 李鸿渐 李志聪 姚然 王兵 李盼盼 李璟 伊晓燕 王军喜 李晋闽 《Journal of Semiconductors》 EI CAS CSCD 2012年第11期24-27,共4页
The growth process of three-dimensional growth mode(3D) switching to two-dimensional growth mode (2D) is investigated when GaN films are grown on cone-shaped patterned sapphire substrates by metal-organic chemical... The growth process of three-dimensional growth mode(3D) switching to two-dimensional growth mode (2D) is investigated when GaN films are grown on cone-shaped patterned sapphire substrates by metal-organic chemical vapor deposition.The growth condition of the 3D-2D growth process is optimized to reduce the threading dislocation density(TDD).It is found that the condition of the 3D layer is critical.The 3D layer keeps growing under the conditions of lowⅤ/Ⅲratio,low temperature,and high pressure until its thickness is comparable to the height of the cone-shaped patterns.Then the 3D layer surrounds the cone-shaped patterns and has inclined side facets and a top(0001) plane.In the following 2D-growth process,inclined side facets coalesce quickly and the interaction of TDs with the side facets causes the TDs to bend over.As a result,the TDD of GaN films can decrease to 1×10~8 cm^(-2),giving full-width at half maximum values of 211 and 219 arcsec for(002) and(102) omega scans, respectively. 展开更多
关键词 threading dislocation GaN pattern sapphire substrate metal organic chemical vapor deposition
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Microstructures of InN film on 4H-SiC(0001) substrate grown by RF-MBE 被引量:3
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作者 P.Jantawongrit S.Sanorpim +2 位作者 H.Yaguchi M.Orihara P.Limsuwan 《Journal of Semiconductors》 EI CAS CSCD 2015年第8期37-41,共5页
InN film was grown on 4H-SiC (0001) substrate by RF plasma-assisted molecular beam epitaxy (RF- MBE). Prior to the growth of InN film, an InN buffer layer with a thickness of ~5.5 nm was grown on the substrate. S... InN film was grown on 4H-SiC (0001) substrate by RF plasma-assisted molecular beam epitaxy (RF- MBE). Prior to the growth of InN film, an InN buffer layer with a thickness of ~5.5 nm was grown on the substrate. Surface morphology, microstructure and structural quality of InN film were investigated. Micro-structural defects, such as stacking faults and anti-phase domain in InN film were carefully investigated using transmission electron microscopy (TEM). The results show that a high density of line contrasts, parallel to the growth direction (c-axis), was clearly observed in the grown InN film. Dark field TEM images recorded with diffraction vectors g = 1120 and g = 0002 revealed that such line contrasts evolved from a coalescence of the adjacent rnisoriented islands during the initial stage of the InN nucleation on the substrate surface. This InN nucleation also led to a generation of anti-phase domains. 展开更多
关键词 RF-MBE TEM INN threading dislocation anti-phase domain crystal polarity
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An InGaAs graded buffer layer in solar cells
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作者 屈晓声 包鸿音 +2 位作者 哈尼 熊丽玲 甄红欣 《Journal of Semiconductors》 EI CAS CSCD 2014年第1期74-77,共4页
This paper uses an InGaAs graded buffer layer to solve the problem of lattice mismatch and device performance degradation. In the graded buffer layer, we choose the "transition layer" and the "cover layer" to acco... This paper uses an InGaAs graded buffer layer to solve the problem of lattice mismatch and device performance degradation. In the graded buffer layer, we choose the "transition layer" and the "cover layer" to accommodate the 3.9% mismatch. No threading dislocations were observed in the uppermost part of the epitaxial layer stack when using a transmission electron microscope (TEM). We analyze the factors which influence the saturation current. Simulation data shows that the cells grown by metal organic vapor phase epitaxy (MOVPE) have considerable open circuit voltage, short circuit current, and photoelectric conversion efficiency. Finally we propose that InP may have great development potential as a substrate material. 展开更多
关键词 solar cells lattice mismatch graded buffer layer threading dislocation carrier lifetime
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The growth and characterization of GaN films on cone-shaped patterned sapphire by MOCVD
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作者 井亮 肖红领 +6 位作者 王晓亮 王翠梅 邓庆文 李志东 丁杰钦 王占国 侯洵 《Journal of Semiconductors》 EI CAS CSCD 2013年第11期20-24,共5页
GaN films are grown on cone-shaped patterned sapphire substrates (CPSSs) by metal-organic chemical vapor deposition, and the influence of the temperature during the middle stage of GaN growth on the threading disloc... GaN films are grown on cone-shaped patterned sapphire substrates (CPSSs) by metal-organic chemical vapor deposition, and the influence of the temperature during the middle stage of GaN growth on the threading dislocation (TD) density of GaN is investigated. High-resolution X-ray diffraction (XRD) and cathodeluminescence (CL) were used to characterize the GaN films. The XRD results showed that the edge-type dislocation density of GaN grown on CPSS is remarkably reduced compared to that of GaN grown on conventional sapphire substrates (CSSs). Furthermore, when the growth temperature in the middle stage of GaN grown on CPSS decreases, the full width at half maximum of the asymmetry (102) plane of GaN is reduced. This reduction is attributed to the enhancement of vertical growth in the middle stage with a more triangular-like shape and the bending of TDs. The CL intensity spatial mapping results also showed the superior optical properties of GaN grown on CPSS to those of GaN on CSS, and that the density of dark spots of GaN grown on CPSS induced by nonradiative recombination is reduced when the growth temperature in the middle stage decreases. 展开更多
关键词 GAN threading dislocation patterned sapphire substrate metal-organic chemical vapor deposition
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