共查询到20条相似文献,搜索用时 31 毫秒
1.
Suk Choi Hee Jin KimJae-Hyun Ryou Russell D. Dupuis 《Journal of Crystal Growth》2009,311(12):3252-3256
We propose a new growth scheme of digitally alloyed modulated precursor flow epitaxial growth (DA-MPEG) using metalorganic and hydride precursors for the growth of AlxGa1−xN layers with high-Al content at relatively low temperatures. The growth of high-quality, high-Al content AlxGa1−xN layers (xAl>50%) that are composed of AlN and AlyGa1−yN monolayers on AlN/sapphire template/substrates by DA-MPEG was demonstrated. The overall composition of the ternary AlxGa1−xN material by DA-MPEG can be controlled continuously by adjusting the Column III mole fraction of the atomic AlyGa1−yN sub-layer. X-ray diffraction and optical transmittance results show that the AlGaN materials have good crystalline quality. The surface morphology of DA-MPEG AlGaN samples measured by atomic force microscopy are comparable to high-temperature-grown AlGaN and are free from surface features such as nano-pits. 相似文献
2.
J.R. Grandusky J.A. Smart M.C. Mendrick L.J. Schowalter K.X. Chen E.F. Schubert 《Journal of Crystal Growth》2009,311(10):2864-2866
Recently it has been discovered that when growing AlxGa1−xN on low-defect-density bulk AlN substrates pseudomorphic layers can be achieved with a thickness far exceeding the critical thickness as given by the Matthews and Blakeslee model. For instance, the critical thickness of an AlxGa1−xN layer (with x=0.6) is about 40 nm thick. However we have been able to grow layers with this composition that are pseudomorphic with a thickness exceeding the critical thickness by more than an order of magnitude. This work defines the limits of pseudomorphic growth on low defect density, bulk AlN substrates to obtain low defect density, high-power UV LEDs. 相似文献
3.
Heon Song Seon-Ho LeeEun-Su Jang Dong-Wook KimR. Navamathavan Jin Soo KimCheul-Ro Lee 《Journal of Crystal Growth》2009,311(19):4418-4422
InxGa1−xN quantum dots (QDs) were grown on GaN/sapphire (0 0 0 1) substrates by employing nitridation of nano-alloyed droplet (NNAD) method using metal-organic chemical vapor deposition (MOCVD). In+Ga alloy droplets were initially formed by flowing the precursors TMIn and TMGa. Density of the In+Ga alloy droplets was increased with increasing precursors flow rate; however, the droplet size was scarcely changed in the range of about 100–200 nm. Two cases of InxGa1−xN QDs growth were investigated by varying the nitridation time and the growth temperature. It was observed that the InxGa1−xN QDs size can be easily changed by controlling the nitridation process at the temperature between 680 and 700 °C for the time of 5–30 min. Self-assembled InxGa1−xN QDs were successfully grown by employing NNAD method. 相似文献
4.
A. Belousov S. Katrych J. Jun J. Zhang D. Günther Roman Sobolewski J. Karpinski B. Batlogg 《Journal of Crystal Growth》2009,311(16):3971-3974
We have successfully grown bulk, single crystals of AlxGa1−xN with the Al content x ranging from 0.5 to 0.9. Samples were grown from Ga melt under high nitrogen pressure (up to 10 kbar) and at high temperature (up to 1800 °C) using a gas pressure system. The homogeneity and Al content of the crystals were investigated by X-ray diffraction and laser ablation mass spectrometry. On the basis of the high-pressure experiments, the corresponding pressure–temperature (p–T) phase diagram of Al–Ga–N was derived. The bandgap of the material was determined by the femtosecond two-photon absorption autocorrelation method and is equal to 5.81±0.01 eV for the Al0.86Ga0.14N crystals. 相似文献
5.
Toshiaki Asai Kensuke NagataToshiaki Mori Kentaro NagamatsuMotoaki Iwaya Satoshi KamiyamaHiroshi Amano Isamu Akasaki 《Journal of Crystal Growth》2009,311(10):2850-2852
The processes as in title of relaxation of the lattice mismatch and the recovery of crystalline quality in thick AlxGa1−xN on high-temperature-grown AlN were investigated. When x=0.3, rapid lattice relaxation occurred over a few microns, then the crystalline quality gradually recovered over 10 μm. In contrast, when x=0.7, relaxation of the lattice mismatch gradually occurred over 5 μm. 相似文献
6.
Tetsuya Matsubara Ryota SendaDaisuke Iida Motoaki IwayaSatoshi Kamiyama Hiroshi AmanoIsamu Akasaki 《Journal of Crystal Growth》2009,311(10):2926-2928
We succeeded in growing high-crystalline-quality thick (1 0 1¯ 1¯) Ga0.92In0.08N films on a grooved (1 0 1¯ 1¯) GaN/(1 0 1¯ 2¯) 4H-SiC underlying layer. We also fabricated GaInN/GaN multiple quantum wells (MQWs) with a peak wavelength of 580 nm on a high-crystalline-quality thick GaInN film. The photoluminescence intensity of the MQWs is about six times higher than that of MQWs grown on planar GaN and twice as high as that of MQWs grown on a GaN underlying layer having the same grooved structure. 相似文献
7.
InxAl1−xN is a particularly useful group-III nitride alloy because by adjusting its composition it can be lattice matched to GaN. Such lattice-matched layers may find application in distributed Bragg reflectors (DBRs) and high electron mobility transistors (HEMTs). However, compared with other semiconducting nitride alloys, InxAl1-xN has not been researched extensively. In this study, thin InxAl1−xN epilayers were grown by metal-organic vapour phase epitaxy (MOVPE) on GaN and AlyGa1−yN layers. Samples were subjected to annealing at their growth temperature of 790 °C for varying lengths of time, or alternatively to a temperature ramp to 1000 °C. Their subsequent surface morphologies were analysed by atomic force microscopy (AFM). For both unstrained InxAl1−xN epilayers grown on GaN and compressively strained epilayers grown on AlyGa1−yN, surface features and fissures were seen to develop as a consequence of thermal treatment, resulting in surface roughening. It is possible that these features are caused by the loss of In-rich material formed on spinodal decomposition. Additionally, trends seen in the strained InxAl1−xN layers may suggest that the presence of biaxial strain stabilises the alloy by suppressing the spinode and shifting it to higher indium compositions. 相似文献
8.
Calculation of phase diagrams in AlxIn1−xAs/InP,AsxSb1−xAl/InP and AlxIn1−xSb/InSb nano-film systems
The models for calculation of phase diagrams of semiconductor thin films with different substrates were proposed by considering the contributions of strain energy, the self-energy of misfit dislocations and surface energy to Gibbs free energy. The phase diagrams of the AlxIn1−xAs and AsxSb1−xAl thin films grown on the InP (1 0 0) substrate, and the AlxIn1−xSb thin films grown on the InSb (1 0 0) substrate at various thicknesses were calculated. The calculated results indicate that when the thickness of film is less than 1 μm, the strain-induced zinc-blende phase appears, the region of this phase extends with decreasing of the layer thickness, and there is small effect of surface energies of liquid and solid phases on the phase diagrams. 相似文献
9.
Spectrometric and ellipsometric studies of (1 − x)TiO2 · xLn2O3 (Ln = Nd, Sm, Gd, Er, Yb) thin films
Spectrometric and ellipsometric studies of (1 − x)TiO2 · xLn2O3 (Ln = Nd, Sm, Gd, Er, Yb; x = 0.33, 0.5) thin films at room temperature were performed. The obtained dispersion dependences of refractive indices are successfully described by the optical-refractometric relation. The dependence of optical pseudogap and refractive indices on composition and molar mass of the films is investigated. The influence of compositional disordering on the energy width of the exponential absorption edge is studied. 相似文献
10.
We demonstrate hexagonal boron nitride (h-BN) epitaxial growth on Ni(1 1 1) substrate by molecular beam epitaxy (MBE) at 890 °C. Elemental boron evaporated by an electron-beam gun and active nitrogen generated by a radio-frequency (RF) plasma source were used as the group-III and -V sources, respectively. Reflection high-energy electron diffraction revealed a streaky (1×1) pattern, indicative of an atomically flat surface in the ongoing growth. Correspondingly, atomic force microscopy images exhibit atomically smooth surface of the resulting h-BN film. X-ray diffraction characterization confirmed the crystallinity of the epitaxial film to be h-BN, and its X-ray rocking curve has a full-width at half-maximum of 0.61°, which is the narrowest ever reported for h-BN thin film. The epitaxial alignments between the h-BN film and the Ni substrate were determined to be [0 0 0 1]h−BN∥[1 1 1]Ni, [1 1 2¯ 0]h−BN∥[1¯ 1 0]Ni, and [1 1¯ 0 0]h−BN∥[1¯ 1¯ 2]Ni. 相似文献
11.
First-principles molecular dynamics (MD) simulations are performed to study the structure and dynamics of liquid Al1−xSix (x = 0.0, 0.12, 0.2, 0.4, 0.6, 0.8) at the temperature of 1573 K. The composition dependence of static structure factors, pair correlation functions, and diffusion constants are investigated. We found that the structure of the liquid Al1−xSix alloys is strongly dependent on the composition. From our simulation and analysis, we can see that although liquid Al1−xSix is metallic, there are some degrees of covalent tetrahedral short-range order in the liquid. The degree of tetrahedral short-range order increases linearly as the Si concentration in the liquid increased. The diffusion coefficients of both Al and Si atoms in liquid Al1−xSix alloys at 1573 K are not very sensitive to the composition. 相似文献
12.
Jung-Hyun Kim Seok Kyu Han Soon-Ku Hong Jae Wook Lee Jeong Yong Lee Jung-Hoon Song Sun Ig Hong Takafumi Yao 《Journal of Crystal Growth》2010,312(15):2190-2195
Single crystalline ZnO film was grown on (1 1 1) Si substrate through employing an oxidized CrN buffer layer by plasma-assisted molecular beam epitaxy. Single crystalline characteristics were confirmed from in-situ reflection high energy electron diffraction, X-ray pole figure measurement, and transmission electron diffraction pattern, consistently. Epitaxial relationship between ZnO film and Si substrate is determined to be (0 0 0 1)ZnO‖(1 1 1)Si and [1 1 2¯ 0]ZnO‖[0 1 1]Si. Full-width at half-maximums (FWHMs) of (0 0 0 2) and (1 0 1¯ 1) X-ray rocking curves (XRCs) were 1.379° and 3.634°, respectively, which were significantly smaller than the FWHMs (4.532° and 32.8°, respectively) of the ZnO film grown directly on Si (1 1 1) substrate without any buffer. Total dislocation density in the top region of film was estimated to be ∼5×109 cm−2. Most of dislocations have a screw type component, which is different from the general cases of ZnO films with the major threading dislocations with an edge component. 相似文献
13.
T.B. Wei Q. HuR.F. Duan X.C. WeiZ.Q. Huo J.X. WangY.P. Zeng G.H. WangJ.M. Li 《Journal of Crystal Growth》2009,311(17):4153-4157
The crystalline, surface, and optical properties of the (1 0 1¯ 3¯) semipolar GaN directly grown on m-plane sapphire substrates by hydride vapor phase epitaxy (HVPE) were investigated. It was found that the increase of V/III ratio led to high quality (1 0 1¯ 3¯) oriented GaN epilayers with a morphology that may have been produced by step-flow growth and with minor evidence of anisotropic crystalline structure. After etching in the mixed acids, the inclined pyramids dominated the GaN surface with a density of 2×105 cm−2, revealing the N-polarity characteristic. In the low-temperature PL spectra, weak BSF-related emission at 3.44 eV could be observed as a shoulder of donor-bound exciton lines for the epilayer at high V/III ratio, which was indicative of obvious reduction of BSFs density. In comparison with other defect related emissions, a different quenching behavior was found for the 3.29 eV emission, characterized by the temperature-dependent PL measurement. 相似文献
14.
A high-energy X-ray diffraction study has been carried out on a series of 0.5Li2S + 0.5[(1 − x)GeS2 + xGeO2] glasses with x = 0.0, 0.1, 0.2, 0.4, 0.6 and 0.8. Structure factors were measured to wave vectors as high as 30 Å−1 resulting in atomic pair distribution functions with high real space resolution. The three dimensional atomic-scale structure of the glasses was modeled by reverse Monte Carlo simulations based on the diffraction data. Results from the simulations show that at the atomic-scale 0.5Li2S + 0.5[(1 − x)GeS2 + xGeO2] glasses may be viewed as an assembly of independent chains of (Li+-S)2GeS2/2 and (Li+-O)2GeO2/2 tetrahedra as repeat units, where the Li ions occupy the open space between the chains. The new structure data may help understand the reasons for the sharp maximum in the Li+ ion conductivity at x ∼ 0.2. 相似文献
15.
Robert Kúdela Michal KučeraEdmund Dobročka Ján Šoltýs 《Journal of Crystal Growth》2009,311(11):3123-3129
Al0.3Ga0.7As/In1−xGaxP structures were prepared by low-pressure MOVPE. Lattice matched and strained ones with top In1−xGaxP layers as well as reverse ones with top Al0,3Ga0,7As layers were examined. The structures were studied by photoluminescence, X-ray and atomic force microscope (AFM) methods. An additional photoluminescence peak from the Al0.3Ga0.7As/In1−xGaxP interface was observed in our samples and it was attributed to a type-II band offset. A conduction band offset of 0.121 eV was measured in the Al0.3Ga0.7As/In0.485Ga0.515P lattice-matched structure and a linear dependence of the conduction band offset on In1−xGaxP composition, with a zero offset in the Al0.3Ga0.7As/In0.315Ga0.685P structure, was determined. The valence band discontinuity had a nearly constant value of 0.152 eV. 相似文献
16.
A. Gouyé O. Kermarrec A. Halimaoui Y. Campidelli D. Rouchon M. Burdin P. Holliger D. Bensahel 《Journal of Crystal Growth》2009,311(13):3522-3527
Si homo-epitaxial growth by low-temperature reduced pressure chemical vapor deposition (RPCVD) using trisilane (Si3H8) has been investigated. The CVD growth of Si films from trisilane and silane on Si substrates are compared at temperatures between 500 and 950 °C. It is demonstrated that trisilane efficiency increases versus silane's one as the surface temperature decreases. Si epilayers from trisilane, with low surface roughness, are achieved at 600 and 550 °C with a growth rate equal to 12.4 and 4.3 nm min−1, respectively. It is also shown that Si1−xGex layers can be deposited using trisilane chemistry. 相似文献
17.
The well known and characterized fast ion conducting (FIC) LiI + Li2S + GeS2 glass-forming system has been further optimized for higher ionic conductivity and improved thermal and chemical stability required for next generation solid electrolyte applications by doping with Ga2S3 and La2S3. These trivalent dopants are expected to eliminate terminal and non-bridging sulfur (NBS) anions thereby increasing the network connectivity while at the same time increasing the Li+ ion conductivity by creating lower basicity [(Ga or La)S4/2]− anion sites. Consistent with the finding that the glass-forming range for the Ga2S3 doped compositions is larger than that for the La2S3 compositions, the addition of Ga2S3 is found to eliminate NBS units to create bridging sulfur (BS) units that not only gives an improvement to the thermal stability, but also maintains and in some cases increases the ionic conductivity. The compositions with the highest Ga2S3 content showed the highest Tgs of ∼325 °C. The addition of La2S3 to the base glasses, by comparison, is found to create NBS by forming high coordination octahedral LaS63− sites, but yet still improved the chemical stability of the glass in dry air and retained its high ionic conductivity and thermal stability. Significantly, at comparable concentrations of Li2S and Ga2S3 or La2S3, the La2S3-doped glasses showed the higher conductivities. The addition of the LiI to the glass compositions not only improved the glass-forming ability of the compositions, but also increased the ionic conductivity glasses. LiI concentrations from 0 to 40 mol% improved the conductivities of the Ga2S3 glasses from ∼10−5 to ∼10−3 (Ω cm)−1 and of the La2S3 glasses from ∼10−4 to ∼10−3 (Ω cm)−1 at room temperature. A maximum conductivity of ∼10−3 (Ω cm)−1 at room temperature was observed for all of the glasses and this value is comparable to some of the best Li ion conductors in a sulfide glass system. Yet these new compositions are markedly more thermally and chemically stable than most Li+ ion conducting sulfide glasses. LiI additions decreased the Tgs and Tcs of the glasses, but increased the stability towards crystallization (Tc − Tg). 相似文献
18.
Transport property and structural investigation have been carried out on newly synthesized Ag+ ion conducting composite electrolyte system. The composite electrolyte system (1 − x)[0.75AgI:0.25AgCl]:xTiO2, where 0 ? x ? 0.5 (in molar weight fraction) has been synthesized by melt quenching and annealing methods. The chemical compound TiO2 (second phase dispersoid) dispersed in different compositions in a quenched (0.75AgI:0.25AgCl) mixed system/solid solution; this solid solution was used as a first phase host salt in place of AgI. The different preparation routes were adopted for the composite electrolyte system. Composition x = 0.1 exhibited highest conductivity at room temperature. The composite system 0.9[0.75AgI:0.25AgCl]:0.1TiO2 was synthesized at different soaking times by melt quenching method. The system exhibited optimum conductivity at 20 min soaking time (σrt ≈ 1.4 × 10−3 S/cm). The ac conductivity has been measured from Z′-Z″ (Cole-Cole) complex impedance plots using impedance spectroscopic (IS) technique. The electrical conductivity as a function of temperature and frequency has been studied, and activation energy Ea, was calculated from Arrhenius plots for all compositions (0 ? x ? 0.5). The dc conductivity value has been evaluated from Log σ vs. log f plots. Structural characterization studies were carried out by X-ray diffraction (XRD) and differential thermal analysis (DSC) techniques. 相似文献
19.
T. Wernicke U. Zeimer C. Netzel F. Brunner A. Knauer M. Weyers M. Kneissl 《Journal of Crystal Growth》2009,311(10):2895-2898
Epitaxial lateral overgrowth was applied to a-plane GaN on r-plane sapphire using SiO2 stripe masks oriented parallel to [0 1¯ 1 1]. Coalescence and defect distribution was studied using scanning electron microscopy and cathodoluminescence. Defects, i.e., threading dislocations and basal plane stacking faults from the template propagate into the overgrown layer through the mask openings. Stacking faults spread into the whole overgrown layer, whereas threading dislocations are laterally confined in the region above the mask where a part of them is terminated at the inclined coalescence boundary. Lateral overgrowth and dislocation termination at the coalescence boundary leads to an improvement in luminescence intensity and crystal quality, in comparison to the template. The measured XRD rocking curve FWHM were 453″ with incidence along the [0 0 0 1] c-direction and 280″ with incidence along the [0 1 1¯ 0] m-direction. 相似文献
20.
In this study, we have investigated the effect of substituting Mn for Fe on the crystallization kinetics of amorphous Fe73.5−xMnxCu1Nb3Si13.5B9 (x = 1, 3, 5, 7) alloys. The samples were annealed at 550 °C and 600 °C for 1 h under an argon atmosphere. The X-ray diffraction analyses showed only a crystalline peak belonging to the α-Fe(Si) phase, with the grain size ranging from 12.2 nm for x = 0 to 16.7 nm for x = 7. The activation energies of the alloys were calculated using Kissinger, Ozawa and Augis-Bennett models based on differential thermal analysis data. The Avrami exponent n was calculated from the Johnson-Mehl-Avrami equation. The activation energy increased up to x = 3, then decreased with increasing Mn content. The values of the Avrami exponent showed that the crystallization is typical diffusion-controlled three-dimensional growth at a constant nucleation rate. 相似文献